8-K 1 csf04ar7_nov.txt NOVEMBER 8K UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington D. C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of The Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): November 26, 2004 CREDIT SUISSE FIRST BOSTON MORTGAGE SECURITIES CORPORATION Mortgage-Backed P/T Certificates, Series 2004-AR7 Trust (Exact name of registrant as specified in its charter) New York (governing law of 333-107055-32 54-2157818 Pooling and Servicing Agreement) (Commission 54-2157819 (State or other File Number) 54-2157820 jurisdiction 54-2157821 of Incorporation) 54-2157822 IRS EIN c/o Wells Fargo Bank, N.A. 9062 Old Annapolis Road Columbia, MD 21045 (Address of principal executive offices) (Zip Code) Registrant's telephone number, including area code: (410) 884-2000 (Former name or former address, if changed since last report) Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below): [ ] Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425) [ ] Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12) [ ] Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act(17 CFR 240.14d-2(b)) [ ] Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act(17 CFR 240.13e-4(c)) ITEM 8.01 Other Events On November 26, 2004 a distribution was made to holders of CREDIT SUISSE FIRST BOSTON MORTGAGE SECURITIES CORPORATION, Mortgage-Backed P/T Certificates, Series 2004-AR7 Trust. ITEM 9.01 Financial Statements and Exhibits (c) Exhibits Exhibit Number Description EX-99.1 Monthly report distributed to holders of Mortgage-Backed P/T Certificates, Series 2004-AR7 Trust, relating to the November 26, 2004 distribution. Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized. CREDIT SUISSE FIRST BOSTON MORTGAGE SECURITIES CORPORATION Mortgage-Backed P/T Certificates, Series 2004-AR7 Trust (Registrant) By: Wells Fargo Bank, N.A. as Trust Administrator By: /s/ Beth Belfield as Assistant Vice President By: Beth Belfield as Assistant Vice President Date: 12/4/2004 INDEX TO EXHIBITS Exhibit Number Description EX-99.1 Monthly report distributed to holders of Mortgage-Backed P/T Certificates, Series 2004-AR7 Trust, relating to the November 26, 2004 distribution. EX-99.1

~~SECURITIES~~Credit ~~AND~~Suisse ~~EXCHANGE~~First ~~COMMISSION~~Boston Mortgage Securities Corp. Mortgage Pass-Through Certificates Record Date: 10/31/2004 Distribution Date: 11/26/2004 CSF Series: 2004-AR7 Contact: Customer Service - SecuritiesLink Wells Fargo Bank, N.A. Securities Administration Services 7485 New Horizon Way Frederick, MD 21703 Telephone: (301) 846-8130 Fax: (301) 815-6660 Certificateholder Distribution Summary Certificate Certificate Beginning Class Pass-Through Certificate Interest Principal Class CUSIP Description Rate Balance Distribution Distribution 1-A-1 22541SRN0 SEN 4.29598% 93,261,008.17 333,873.16 2,403,160.66 AR 22541SSG4 RES 4.28960% 0.00 0.00 0.00 AR-L 22541SSH2 RES 4.28960% 0.00 0.00 0.00 2-A-1 22541SRP5 SEN 4.89335% 277,945,251.96 1,133,402.58 8,146,132.85 3-A-1 22541SRQ3 SEN 4.33824% 92,641,213.39 334,916.33 1,863,878.49 4-A-1 22541SRR1 SEN 4.69563% 207,039,962.26 810,153.41 3,769,968.71 5-A-1 22541SRS9 SEN 4.26946% 95,908,323.42 341,230.75 1,913,903.02 6-A-1 22541SRT7 SEN 2.30250% 184,514,943.50 377,640.58 5,432,989.07 6-A-2 22541SRU4 SEN 2.31250% 187,660,777.00 385,747.15 8,253,515.70 6-A-3 22541SRV2 SEN 2.17250% 74,505,565.58 143,878.53 4,527,212.99 6-A-4 22541SRW0 SEN 2.48250% 28,430,000.00 62,735.54 0.00 6-A-5 22541SRX8 SEN 2.25250% 27,152,615.56 54,365.57 1,194,200.21 6-M-1 22541SRY6 MEZ 2.58250% 29,360,000.00 67,397.51 0.00 6-M-2 22541SRZ3 MEZ 3.33250% 11,085,000.00 32,836.23 0.00 6-M-3 22541SSA7 MEZ 4.18250% 8,988,000.00 33,415.39 0.00 6-M-4 22541SSB5 MEZ 4.68250% 2,996,147.21 12,470.63 0.00 C-B-1 22541SSC3 JUN 2.58250% 48,018,956.86 110,230.18 20,468.80 C-B-1X 22541SSF6 JUN-IO 1.86644% 0.00 74,687.03 0.00 C-B-2 22541SSD1 JUN 4.62111% 13,098,348.98 50,440.71 5,583.37 C-B-3 22541SSE9 JUN 4.62111% 7,858,010.66 30,260.58 3,349.59 C-B-4 22541SRJ9 JUN 4.62111% 3,054,117.51 11,761.17 1,301.86 C-B-5 22541SRK6 JUN 4.62111% 3,930,004.06 15,134.14 1,675.22 C-B-6 22541SRL4 JUN 4.62111% 2,616,517.80 10,076.00 1,115.33 6-X 22541SRM2 OC 0.00000% 2,995,945.74 1,526,696.35 0.00 Totals 1,403,060,709.66 5,953,349.52 37,538,455.87

~~Washington~~Certificateholder Distribution Summary (continued) Current Ending Cumulative Realized Certificate Total Realized Class Loss Balance Distribution Losses 1-A-1 0.00 90,857,847.50 D2,737,033.82 0.00 AR 0.00 0.00 0.00 0.00 AR-L 0.00 0.00 0.00 0.00 2-A-1 0.00 269,799,119.10 9,279,535.43 0.00 3-A-1 0.00 90,777,334.90 2,198,794.82 0.00 4-A-1 0.00 203,269,993.55 4,580,122.12 0.00 5-A-1 0.00 93,994,420.40 2,255,133.77 0.00 6-A-1 0.00 179,081,954.43 5,810,629.65 0.00 6-A-2 0.00 179,407,261.30 8,639,262.85 0.00 6-A-3 0.00 69,978,352.60 4,671,091.52 0.00 6-A-4 0.00 28,430,000.00 62,735.54 0.00 6-A-5 0.00 25,958,415.35 1,248,565.78 0.00 6-M-1 0.00 29,360,000.00 67,397.51 0.00 6-M-2 0.00 11,085,000.00 32,836.23 0.00 6-M-3 0.00 8,988,000.00 33,415.39 0.00 6-M-4 0.00 2,996,147.21 12,470.63 0.00 C-B-1 0. ~~20549~~00 47,998,488.06 130,698.98 0.00 C-B-1X 0.00 0.00 74,687.03 0.00 C-B-2 0.00 13,092,765.62 56,024.08 0.00 C-B-3 0.00 7,854,661.07 33,610.17 0.00 C-B-4 0.00 3,052,815.65 13,063.03 0.00 C-B-5 0.00 3,928,328.84 16,809.36 0.00 C-B-6 0.00 2,615,402.47 11,191.33 0.00 6-X 0.00 2,995,945.74 1,526,696.35 0.00 Totals 0.00 1,365,522,253.79 43,491,805.39 0.00 All distributions required by the Pooling and Servicing Agreement have been calculated by the Certificate Administrator on behalf of the Trustee.

~~Form~~Principal Distribution Statement Original Beginning Scheduled Unscheduled Face Certificate Principal Principal Realized Class Amount Balance Distribution Distribution Accretion Loss (1) 1-A-1 98,710,000.00 93,261,008.17 36,190.62 2,366,970.04 0.00 0.00 AR 50.00 0.00 0.00 0.00 0.00 0.00 AR-L 50.00 0.00 0.00 0.00 0.00 0.00 2-A-1 287,200,000.00 277,945,251.96 107,805.96 8,038,326.89 0.00 0.00 3-KA-1 97,550,000.00 92,641,213.39 59,681.07 1,804,197.42 0.00 0.00 4-A-1 214,050,000.00 207,039,962.26 107,624.96 3,662,343.75 0.00 0.00 5-A-1 98,040,000.00 95,908,323.42 15,037.34 1,898,865.68 0.00 0.00 6-A-1 195,690,000.00 184,514,943.50 0.00 5,432,989.07 0.00 0.00 6-A-2 207,340,000.00 187,660,777.00 0.00 8,253,515.70 0.00 0.00 6-A-3 85,300,000.00 74,505,565.58 0.00 4,527,212.99 0.00 0.00 6-A-4 28,430,000.00 28,430,000.00 0.00 0.00 0.00 0.00 6-A-5 30,000,000.00 27,152,615.56 0.00 1,194,200.21 0.00 0.00 6-M-1 29,360,000.00 29,360,000.00 0.00 0.00 0.00 0.00 6-M-2 11,085,000.00 11,085,000.00 0.00 0.00 0.00 0.00 6-M-3 8,988,000.00 8,988,000.00 0.00 0.00 0.00 0.00 6-M-4 2,996,147.21 2,996,147.21 0.00 0.00 0.00 0.00 C-B-1 48,080,000.00 48,018,956.86 20,468.80 0.00 0.00 0.00 C-B-1X 0.00 0.00 0.00 0.00 0.00 0.00 C-B-2 13,115,000.00 13,098,348.98 5,583.37 0.00 0.00 0.00 C-B-3 7,868,000.00 7,858,010.66 3,349.59 0.00 0.00 0.00 C-B-4 3,058,000.00 3,054,117.51 1,301.86 0.00 0.00 0.00 C-B-5 3,935,000.00 3,930,004.06 1,675.22 0.00 0.00 0.00 C-B-6 2,619,844.00 2,616,517.80 1,115.33 0.00 0.00 0.00 6-X 0.00 2,995,945.74 0.00 0.00 0.00 0.00 Totals 1,473,415,091.21 1,403,060,709.66 359,834.12 37,178,621.75 0.00 0.00 (1) Amount Does Not Include Excess Special Hazard, Bankruptcy, or Fraud Losses Unless Otherwise Disclosed. Please Refer to the Prospectus Supplement for a Full Description.

~~CURRENT~~Principal ~~REPORT~~Distribution Statement (continued) Total Ending Ending Total Principal Certificate Certificate Principal Class Reduction Balance Percentage Distribution 1-A-1 2,403,160.66 90,857,847.50 0.92045231 2,403,160.66 AR 0.00 0.00 0.00000000 0.00 AR-L 0.00 0.00 0.00000000 0.00 2-A-1 8,146,132.85 269,799,119.10 0.93941197 8,146,132.85 3-A-1 1,863,878.49 90,777,334.90 0.93057237 1,863,878.49 4-A-1 3,769,968.71 203,269,993.55 0.94963790 3,769,968.71 5-A-1 1,913,903.02 93,994,420.40 0.95873542 1,913,903.02 6-A-1 5,432,989.07 179,081,954.43 0.91513084 5,432,989.07 6-A-2 8,253,515.70 179,407,261.30 0.86528051 8,253,515.70 6-A-3 4,527,212.99 69,978,352.60 0.82037928 4,527,212.99 6-A-4 0.00 28,430,000.00 1.00000000 0.00 6-A-5 1,194,200.21 25,958,415.35 0.86528051 1,194,200.21 6-M-1 0.00 29,360,000.00 1.00000000 0.00 6-M-2 0.00 11,085,000.00 1.00000000 0.00 6-M-3 0.00 8,988,000.00 1.00000000 0.00 6-M-4 0.00 2,996,147.21 1.00000000 0.00 C-B-1 20,468.80 47,998,488.06 0.99830466 20,468.80 C-B-1X 0.00 0.00 0.00000000 0.00 C-B-2 5,583.37 13,092,765.62 0.99830466 5,583.37 C-B-3 3,349.59 7,854,661.07 0.99830466 3,349.59 C-B-4 1,301.86 3,052,815.65 0.99830466 1,301.86 C-B-5 1,675.22 3,928,328.84 0.99830466 1,675.22 C-B-6 1,115.33 2,615,402.47 0.99830466 1,115.33 6-X 0.00 2,995,945.74 0.00000000 0.00 Totals 37,538,455.87 1,365,522,253.79 0.92677363 37,538,455.87

~~Pursuant~~Principal toDistribution ~~Section~~Factors 13Statement orOriginal 15Beginning Scheduled Unscheduled Face Certificate Principal Principal Class (d2) ofAmount ~~the~~Balance Distribution Distribution Accretion 1-A-1 98,710,000.00 944.79797559 0.36663580 23.97902989 0.00000000 AR 50.00 0.00000000 0.00000000 0.00000000 0.00000000 AR-L 50.00 0.00000000 0.00000000 0.00000000 0.00000000 2-A-1 287,200,000.00 967.77594694 0.37536894 27.98860338 0.00000000 3-A-1 97,550,000.00 949.67927617 0.61179979 18.49510425 0.00000000 4-A-1 214,050,000.00 967.25046606 0.50280290 17.10975823 0.00000000 5-A-1 98,040,000.00 978.25707283 0.15337964 19.36827499 0.00000000 6-A-1 195,690,000.00 942.89408503 0.00000000 27.76324324 0.00000000 6-A-2 207,340,000.00 905.08718530 0.00000000 39.80667358 0.00000000 6-A-3 85,300,000.00 873.45328933 0.00000000 53.07400926 0.00000000 6-A-4 28,430,000.00 1000.00000000 0.00000000 0.00000000 0.00000000 6-A-5 30,000,000.00 905.08718533 0.00000000 39.80667367 0.00000000 6-M-1 29,360,000.00 1000.00000000 0.00000000 0.00000000 0.00000000 6-M-2 11,085,000.00 1000.00000000 0.00000000 0.00000000 0.00000000 6-M-3 8,988,000.00 1000.00000000 0.00000000 0.00000000 0.00000000 6-M-4 2,996,147.21 1000.00000000 0.00000000 0.00000000 0.00000000 C-B-1 48,080,000.00 998.73038394 0.42572379 0.00000000 0.00000000 C-B-1X 0.00 0.00000000 0.00000000 0.00000000 0.00000000 C-B-2 13,115,000.00 998.73038353 0.42572398 0.00000000 0.00000000 C-B-3 7,868,000.00 998.73038383 0.42572318 0.00000000 0.00000000 C-B-4 3,058,000.00 998.73038260 0.42572269 0.00000000 0.00000000 C-B-5 3,935,000.00 998.73038374 0.42572300 0.00000000 0.00000000 C-B-6 2,619,844.00 998.73038242 0.42572382 0.00000000 0.00000000 6-X 0.00 0.00000000 0.00000000 0.00000000 0.00000000

~~Securities~~Principal ~~Exchange~~Distribution ~~Act~~Factors ofStatement ~~1934~~(continued) Total Ending Ending Total Realized Principal Certificate Certificate Principal Class Loss (3) Reduction Balance Percentage Distribution 1-A-1 0.00000000 24.34566569 920.45230980 0.92045231 24.34566569 AR 0.00000000 0.00000000 0.00000000 0.00000000 0.00000000 AR-L 0.00000000 0.00000000 0.00000000 0.00000000 0.00000000 2-A-1 0.00000000 28.36397232 939.41197458 0.93941197 28.36397232 3-A-1 0.00000000 19.10690405 930.57237212 0.93057237 19.10690405 4-A-1 0.00000000 17.61256113 949.63790493 0.94963790 17.61256113 5-A-1 0.00000000 19.52165463 958.73541820 0.95873542 19.52165463 6-A-1 0.00000000 27.76324324 915.13084179 0.91513084 27.76324324 6-A-2 0.00000000 39.80667358 865.28051172 0.86528051 39.80667358 6-A-3 0.00000000 53.07400926 820.37928019 0.82037928 53.07400926 6-A-4 0.00000000 0.00000000 1,000.00000000 1.00000000 0.00000000 6-A-5 0.00000000 39.80667367 865.28051167 0.86528051 39.80667367 6-M-1 0.00000000 0.00000000 1,000.00000000 1.00000000 0.00000000 6-M-2 0.00000000 0.00000000 1,000.00000000 1.00000000 0.00000000 6-M-3 0.00000000 0.00000000 1,000.00000000 1.00000000 0.00000000 6-M-4 0.00000000 0.00000000 1,000.00000000 1.00000000 0.00000000 C-B-1 0.00000000 0.42572379 998.30466015 0.99830466 0.42572379 C-B-1X 0.00000000 0.00000000 0.00000000 0.00000000 0.00000000 C-B-2 0.00000000 0.42572398 998.30466031 0.99830466 0.42572398 C-B-3 0.00000000 0.42572318 998.30466065 0.99830466 0.42572318 C-B-4 0.00000000 0.42572269 998.30465991 0.99830466 0.42572269 C-B-5 0.00000000 0.42572300 998.30466074 0.99830466 0.42572300 C-B-6 0.00000000 0.42572382 998.30465860 0.99830466 0.42572382 6-X 0.00000000 0.00000000 0.00000000 0.00000000 0.00000000 (3) Amount Does Not Include Excess Special Hazard, Bankruptcy, or Fraud Losses Unless Otherwise Disclosed. Please Refer to the Prospectus Supplement for a Full Description.

~~Date~~Interest ofDistribution ~~Report~~Statement ~~(Date~~Beginning Payment of ~~earliest~~Original ~~event~~Current Certificate/ Current Unpaid Current Face Certificate Notional Accrued Interest Interest Class Amount Rate Balance Interest Shortfall Shortfall 1-A-1 98,710,000.00 4.29598% 93,261,008.17 333,873.16 0.00 0.00 AR 50.00 4.28960% 0.00 0.00 0.00 0.00 AR-L 50.00 4.28960% 0.00 0.00 0.00 0.00 2-A-1 287,200,000.00 4.89335% 277,945,251.96 1,133,402.58 0.00 0.00 3-A-1 97,550,000.00 4.33824% 92,641,213.39 334,916.34 0.00 0.00 4-A-1 214,050,000.00 4.69563% 207,039,962.26 810,153.41 0.00 0.00 5-A-1 98,040,000.00 4.26946% 95,908,323.42 341,230.75 0.00 0.00 6-A-1 195,690,000.00 2.30250% 184,514,943.50 377,640.58 0.00 0.00 6-A-2 207,340,000.00 2.31250% 187,660,777.00 385,747.15 0.00 0.00 6-A-3 85,300,000.00 2.17250% 74,505,565.58 143,878.53 0.00 0.00 6-A-4 28,430,000.00 2.48250% 28,430,000.00 62,735.53 0.00 0.00 6-A-5 30,000,000.00 2.25250% 27,152,615.56 54,365.57 0.00 0.00 6-M-1 29,360,000.00 2.58250% 29,360,000.00 67,397.51 0.00 0.00 6-M-2 11,085,000.00 3.33250% 11,085,000.00 32,836.23 0.00 0.00 6-M-3 8,988,000.00 4.18250% 8,988,000.00 33,415.39 0.00 0.00 6-M-4 2,996,147.21 4.68250% 2,996,147.21 12,470.63 0.00 0.00 C-B-1 48,080,000.00 2.58250% 48,018,956.86 110,230.18 0.00 0.00 C-B-1X 0.00 1.86644% 48,018,956.86 74,687.03 0.00 0.00 C-B-2 13,115,000.00 4.62111% 13,098,348.98 50,440.71 0.00 0.00 C-B-3 7,868,000.00 4.62111% 7,858,010.66 30,260.58 0.00 0.00 C-B-4 3,058,000.00 4.62111% 3,054,117.51 11,761.17 0.00 0.00 C-B-5 3,935,000.00 4.62111% 3,930,004.06 15,134.14 0.00 0.00 C-B-6 2,619,844.00 4.62111% 2,616,517.80 10,076.00 0.00 0.00 6-X 0.00 0.00000% 557,688,994.59 0.00 0.00 0.00 Totals 1,473,415,091.21 4,426,653.17 0.00 0.00

~~Reported~~Interest Distribution Statement (continued)~~: October~~ 22Remaining Ending Non-Supported Total Unpaid Certificate/ Interest Realized Interest Interest Notional Class Shortfall Losses (4) Distribution Shortfall Balance 1-A-1 0.00 0.00 333,873.16 ~~2004~~0.00 90,857,847.50 AR 0.00 0.00 0.00 0.00 0.00 AR-L 0.00 0.00 0.00 0.00 0.00 2-A-1 0.00 0.00 1,133,402.58 0.00 269,799,119.10 3-A-1 0.00 0.00 334,916.33 0.00 90,777,334.90 4-A-1 0.00 0.00 810,153.41 0.00 203,269,993.55 5-A-1 0.00 0.00 341,230.75 0.00 93,994,420.40 6-A-1 0.00 0.00 377,640.58 0.00 179,081,954.43 6-A-2 0.00 0.00 385,747.15 0.00 179,407,261.30 6-A-3 0.00 0.00 143,878.53 0.00 69,978,352.60 6-A-4 0.00 0.00 62,735.54 0.00 28,430,000.00 6-A-5 0.00 0.00 54,365.57 0.00 25,958,415.35 6-M-1 0.00 0.00 67,397.51 0.00 29,360,000.00 6-M-2 0.00 0.00 32,836.23 0.00 11,085,000.00 6-M-3 0.00 0.00 33,415.39 0.00 8,988,000.00 6-M-4 0.00 0.00 12,470.63 0.00 2,996,147.21 C-B-1 0.00 0.00 110,230.18 0.00 47,998,488.06 C-B-1X 0.00 0.00 74,687.03 0.00 47,998,488.06 C-B-2 0.00 0.00 50,440.71 0.00 13,092,765.62 C-B-3 0.00 0.00 30,260.58 0.00 7,854,661.07 C-B-4 0.00 0.00 11,761.17 0.00 3,052,815.65 C-B-5 0.00 0.00 15,134.14 0.00 3,928,328.84 C-B-6 0.00 0.00 10,076.00 0.00 2,615,402.47 6-X 0.00 0.00 1,526,696.35 0.00 538,281,076.63 Totals 0.00 0.00 5,953,349.52 0.00 (4) Amount Does Not Include Excess Special Hazard, Bankruptcy, or Fraud Losses Unless Otherwise Disclosed. Please Refer to the Prospectus Supplement for a Full Description.

CREDIT SUISSE FIRST BOSTON MORTGAGE SECURITIES CORP.
(Exact name of registrant as specified in its charter)
Delaware	333-100669	13-3320910
(State or Other Jurisdiction of Incorporation)	(Commission File Number)	(I.R.S. Employer Identification No.)
11 Madison Avenue New York, New York 10010
(Address of Principal Executive Offices) (Zip Code)
Registrant’s telephone number, including area code (212) 325-2000

~~Check~~Interest ~~the~~Distribution ~~appropriate~~Factors ~~box~~Statement ~~below~~(continued) ifRemaining ~~the~~Ending ~~Form~~Non-Supported 8Total Unpaid Certificate/ Interest Realized Interest Interest Notional Class Shortfall Losses (6) Distribution Shortfall Balance 1-KA-1 ~~filing~~0.00000000 is0.00000000 ~~intended~~3.38236410 to0.00000000 ~~simultaneously~~920.45230980 ~~satisfy~~AR ~~the~~0.00000000 ~~filing~~0.00000000 ~~obligation~~0.00000000 of0.00000000 ~~the~~0.00000000 ~~registrant~~AR-L ~~under~~0.00000000 ~~any~~0.00000000 of0.00000000 0.00000000 0.00000000 2-A-1 0.00000000 0.00000000 3.94638781 0.00000000 939.41197458 3-A-1 0.00000000 0.00000000 3.43327863 0.00000000 930.57237212 4-A-1 0.00000000 0.00000000 3.78487928 0.00000000 949.63790493 5-A-1 0.00000000 0.00000000 3.48052581 0.00000000 958.73541820 6-A-1 0.00000000 0.00000000 1.92978987 0.00000000 915.13084179 6-A-2 0.00000000 0.00000000 1.86045698 0.00000000 865.28051172 6-A-3 0.00000000 0.00000000 1.68673540 0.00000000 820.37928019 6-A-4 0.00000000 0.00000000 2.20666690 0.00000000 1000.00000000 6-A-5 0.00000000 0.00000000 1.81218567 0.00000000 865.28051167 6-M-1 0.00000000 0.00000000 2.29555552 0.00000000 1000.00000000 6-M-2 0.00000000 0.00000000 2.96222192 0.00000000 1000.00000000 6-M-3 0.00000000 0.00000000 3.71777815 0.00000000 1000.00000000 6-M-4 0.00000000 0.00000000 4.16222206 0.00000000 1000.00000000 C-B-1 0.00000000 0.00000000 2.29264101 0.00000000 998.30466015 C-B-1X 0.00000000 0.00000000 1.55339081 0.00000000 998.30466015 C-B-2 0.00000000 0.00000000 3.84603202 0.00000000 998.30466031 C-B-3 0.00000000 0.00000000 3.84603203 0.00000000 998.30466065 C-B-4 0.00000000 0.00000000 3.84603336 0.00000000 998.30465991 C-B-5 0.00000000 0.00000000 3.84603304 0.00000000 998.30466074 C-B-6 0.00000000 0.00000000 3.84603053 0.00000000 998.30465860 6-X 0.00000000 0.00000000 0.00000000 0.00000000 0.00000000 (6) Amount Does Not Include Excess Special Hazard, Bankruptcy,or Fraud Losses Unless Otherwise Disclosed. Please Refer to the ~~following~~Prospectus ~~provisions:~~Supplement for a Full Description.

~~Written~~CERTIFICATEHOLDER ~~communications~~ACCOUNT ~~pursuant~~STATEMENT toCERTIFICATE ~~Rule~~ACCOUNT ~~425~~Beginning ~~under~~Balance ~~the~~0.00 ~~Securities~~Deposits ~~Act~~Payments ~~(17~~of ~~CFR~~Interest ~~230~~and Principal 43,867,804.~~425)~~73 ~~Soliciting~~Liquidations, ~~material~~Insurance ~~pursuant~~Proceeds, toReserve ~~Rule~~Funds ~~14a-12~~0.00 ~~under~~Proceeds ~~the~~from ~~Exchange~~Repurchased ~~Act~~Loans 0.00 Other Amounts (17Servicer ~~CFR~~Advances) ~~240~~82,002.~~14a-12)~~55 ~~Pre-commencement~~Realized ~~communications~~Loss ~~pursuant~~(Gains, toSubsequent ~~Rule~~Expenses ~~14d-2(d~~& Recoveries) ~~under~~0.00 ~~the~~Prepayment ~~Exchange~~Penalties ~~Act~~0.00 ~~(17~~Total ~~CFR~~Deposits ~~240~~43,949,807.~~14d-2(b))~~28 ~~Pre-commencement~~Withdrawals ~~communications~~Reimbursement ~~pursuant~~for toServicer ~~Rule~~Advances ~~13e-4(c)~~62,519.17 ~~under~~Payment ~~the~~of ~~Exchange~~Service ~~Act~~Fee ~~(17~~395,482.72 ~~CFR~~Payment ~~240~~of Interest and Principal 43,491,805.~~13e-4~~39 Total Withdrawals (cPool Distribution Amount)) 43,949,807.28 Ending Balance 0.00

~~Item~~PREPAYMENT/CURTAILMENT 9INTEREST SHORTFALL Total Prepayment/Curtailment Interest Shortfall 0.0100 Servicing Fee Support 0.00 Non-Supported Prepayment/Curtailment Interest Shortfall 0.00

~~Financial~~SERVICING ~~Statements~~FEES Gross Servicing Fee 372,874.62 External Master Servicing Fee 19,985.32 PMI Fee 2,622.78 Supported Prepayment/Curtailment Interest Shortfall 0.00 Net Servicing Fee 395,482.72

~~Information~~OTHER ~~and~~ACCOUNTS ~~Exhibits~~Beginning Current Current Ending Account Type Balance Withdrawals Deposits Balance Reserve Fund 5,000.00 0.00 0.00 5,000.00 Reserve Fund 5,000.00 0.00 0.00 5,000.00

~~(a)~~LOAN STATUS STRATIFICATION/CREDIT ENHANCEMENT STATEMENT DELINQUENCY STATUS DELINQUENT BANKRUPTCY FORECLOSURE REO Total No of Loans No of Loans No of Loans No of Loans No of Loans Principal Balance Principal Balance Principal Balance Principal Balance Principal Balance 0-29 Days 0 0 0 0 0.00 0.00 0.00 0.00 30 Days 19 0 0 0 19 7,077,839.99 0.00 0.00 0.00 7,077,839.99 60 Days 26 0 0 0 26 6,309,510.15 0.00 0.00 0.00 6,309,510.15 90 Days 2 0 2 0 4 236,800.00 0.00 377,000.00 0.00 613,800.00 120 Days 2 0 0 0 2 680,800.48 0.00 0.00 0.00 680,800.48 150 Days 1 0 0 0 1 629,014.11 0.00 0.00 0.00 629,014.11 180+ Days 0 0 0 0 0 0.00 0.00 0.00 0.00 0.00 Totals 50 0 2 0 52 14,933,964.73 0.00 377,000.00 0.00 15,310,964.73 No of Loans No of Loans No of Loans No of Loans No of Loans Principal Balance Principal Balance Principal Balance Principal Balance Principal Balance 0-29 Days 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 30 Days 0.378637% 0.000000% 0.000000% 0.000000% 0.378637% 0.518142% 0.000000% 0.000000% 0.000000% 0.518142% 60 Days 0.518135% 0.000000% 0.000000% 0.000000% 0.518135% 0.461896% 0.000000% 0.000000% 0.000000% 0.461896% 90 Days 0.039857% 0.000000% 0.039857% 0.000000% 0.079713% 0.017335% 0.000000% 0.027599% 0.000000% 0.044934% 120 Days 0.039857% 0.000000% 0.000000% 0.000000% 0.039857% 0.049839% 0.000000% 0.000000% 0.000000% 0.049839% 150 Days 0.019928% 0.000000% 0.000000% 0.000000% 0.019928% 0.046048% 0.000000% 0.000000% 0.000000% 0.046048% 180+ Days 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% Totals 0.996413% 0.000000% 0.039857% 0.000000% 1.036269% 1.093260% 0.000000% 0.027599% 0.000000% 1.120859%

Not applicable.

~~(b)~~OTHER INFORMATION Current Period Class A Insufficient Funds 0.00 Principal Balance of Contaminated Properties 0.00 Periodic Advance 82,002.55

~~Not~~CREDIT ~~applicable~~ENHANCEMENT Original $ Original % Current $ Current % Bankruptcy 322,268.00 0.02187218% 322,268.00 0.02360035% Fraud 17,484,519.00 1.18666621% 17,484,519.00 1.28042725% Special Hazard 8,742,260.00 0.59333314% 8,742,260.00 0.64021366% Limit of Subordinate's Exposure to Certain Types of Losses

COLLATERAL STATEMENT Collateral Description Mixed ARM Weighted Average Gross Coupon 5.429985% Weighted Average Net Coupon 5.111075% Weighted Average Pass-Through Rate 5.091739% Weighted Average Maturity(cStepdown Calculation ) 356 Beginning Scheduled Collateral Loan Count 5,127 Number Of Loans Paid In Full 109 Ending Scheduled Collateral Loan Count 5,018 Beginning Scheduled Collateral Balance 1,403,060,710.11 Ending Scheduled Collateral Balance 1,365,522,254.24 Ending Actual Collateral Balance at 31-Oct-2004 1,366,003,088.07 Monthly P &I Constant 6,916,934.50 Special Servicing Fee 0.00 Prepayment Penalties 0.00 Realized Loss Amount 0.00 Cumulative Realized Loss 0.00 Scheduled Principal 568,102.28 Unscheduled Principal 36,970,353.59

~~Exhibits:~~Miscellaneous Reporting Rolling 3 month Delinquency Rate 0.008431% Excess Cash 1,526,696.39 Grp 1 Excess Interest 1,704.44 Grp 1 Excess Interest 3,802.70 Extra Principal Distribution 0.00 Overcollateralized Amount 2,995,945.74 Overcollateralization Deficiency 0.00 Overcollateralization Increase 0.00 Overcollateralization Release 0.00 Target Overcollateralization 2,995,945.74 Trigger Event - 3 mo Delinq Rate > 5.25% NO Grp 4 Prefunding Amount 0.00 Grp 4 Prefunding Balance 0.00 Grp 4 Remaining Prefunding Bal 0.00 Grp 4 Capitalized Interest Added 0.00

Group Level Collateral Statement Group G1 30Y Jumbo A Arm G2 30Y Jumbo A Arm G3 30Y Jumbo A Arm Collateral Description Mixed ARM Mixed ARM Mixed ARM Weighted Average Coupon Rate 4.671922 5.273957 4.733067 Weighted Average Net Rate 4.324914 4.920591 4.374292 Weighted Average Maturity 354 354 354 Beginning Loan Count 207 771 502 Loans Paid In Full 3 16 7 Ending Loan Count 204 755 495 Beginning Scheduled Balance 103,014,706.81 306,329,160.24 102,266,309.35 Ending scheduled Balance 100,607,761.15 298,172,018.19 100,396,230.21 Record Date 10/31/2004 10/31/2004 10/31/2004 Principal And Interest Constant 441,039.54 1,465,120.73 469,242.77 Scheduled Principal 39,975.62 118,815.16 65,881.72 Unscheduled Principal 2,366,970.04 8,038,326.89 1,804,197.42 Scheduled Interest 401,063.92 1,346,305.57 403,361.05 Servicing Fees 29,789.15 90,205.24 30,575.51 Master Servicing Fees 0.00 0.00 0.00 Trustee Fee 0.00 0.00 0.00 FRY Amount 0.00 0.00 0.00 Special Hazard Fee 0.00 0.00 0.00 Other Fee 2,483.51 6,954.13 1,368.15 Pool Insurance Fee 0.00 0.00 0.00 Spread Fee 1 0.00 0.00 0.00 Spread Fee 2 0.00 0.00 0.00 Spread Fee 3 0.00 0.00 0.00 Net Interest 368,791.26 1,249,146.20 371,417.39 Realized Loss Amount 0.00 0.00 0.00 Cumulative Realized Loss 0.00 0.00 0.00 Percentage of Cumulative Losses 0.0000 0.0000 0.0000 Prepayment Penalties 0.00 0.00 0.00 Special Servicing Fee 0.00 0.00 0.00 Pass-Through Rate 4.295984 4.893349 4.358238

~~Tax~~Group ~~Opinion~~Level Collateral Statement Group G4 30Y Jumbo A Arm G5 30Y Jumbo A Arm G6A 30Y Alt A Arm Collateral Description Mixed ARM Mixed ARM Mixed ARM Weighted Average Coupon Rate 5.104646 4.684462 6.055872 Weighted Average Net Rate 4.741973 4.309462 5.798389 Weighted Average Maturity 354 354 354 Beginning Loan Count 1,139 188 1,049 Loans Paid In Full 18 2 27 Ending Loan Count 1,121 186 1,022 Beginning Scheduled Balance 228,162,147.34 105,599,391.78 204,259,983.48 Ending scheduled Balance 224,381,198.75 103,683,969.31 198,826,994.41 Record Date 10/31/2004 10/31/2004 10/31/2004 Principal And Interest Constant 1,089,177.31 428,787.03 1,110,570.83 Scheduled Principal 118,604.84 16,556.79 79,760.59 Unscheduled Principal 3,662,343.75 1,898,865.68 5,353,228.48 Scheduled Interest 970,572.47 412,230.24 1,030,810.24 Servicing Fees 68,956.82 32,999.80 43,827.87 Master Servicing Fees 0.00 0.00 0.00 Trustee Fee 0.00 0.00 0.00 FRY Amount 0.00 0.00 0.00 Special Hazard Fee 0.00 0.00 0.00 Other Fee 5,007.81 3,519.98 1,243.32 Pool Insurance Fee 0.00 0.00 0.00 Spread Fee 1 0.00 0.00 0.00 Spread Fee 2 0.00 0.00 0.00 Spread Fee 3 0.00 0.00 0.00 Net Interest 896,607.84 375,710.46 985,739.05 Realized Loss Amount 0.00 0.00 0.00 Cumulative Realized Loss 0.00 0.00 0.00 Percentage of ~~McKee~~Cumulative ~~Nelson~~Losses ~~LLP~~0.0000 0.0000 0.0000 Prepayment Penalties 0.00 0.00 0.00 Special Servicing Fee 0.00 0.00 0.00 Pass-Through Rate 4.715635 4.269462 5.791085

~~SIGNATURES~~Group Level Collateral Statement Group G6B 30Y Alt A Arm Total Collateral Description Mixed ARM Mixed ARM Weighted Average Coupon Rate 6.058887 5.429985 Weighted Average Net Rate 5.799077 5.111075 Weighted Average Maturity 355.00 356.00 Record Date 10/31/2004 10/31/2004 Principal And Interest Constant 1,912,996.29 6,916,934.50 Beginning Loan Count 1,271 5,127 Loans Paid In Full 36 109 Ending Loan Count 1,235 5,018 Beginning Scheduled Balance 353,429,011.11 1,403,060,710.11 Ending Scheduled Balance 339,454,082.22 1,365,522,254.24 Scheduled Principal 128,507.56 568,102.28 Unscheduled Principal 13,846,421.33 36,970,353.59 Scheduled Interest 1,784,488.73 6,348,832.22 Servicing Fee 76,520.23 372,874.62 Master Servicing Fee 0.00 0.00 Trustee Fee 0.00 0.00 Fry Amount 0.00 0.00 Special Hazard Fee 0.00 0.00 Other Fee 2,031.20 22,608.10 Pool Insurance Fee 0.00 0.00 Spread 1 0.00 0.00 Spread 2 0.00 0.00 Spread 3 0.00 0.00 Net Interest 1,705,937.30 5,953,349.50 Realized Loss Amount 0.00 0.00 Cumulative Realized Loss 0.00 0.00 Percentage of Cumulative Losses 0.0000 0.0000 Prepayment Penalties 0.00 0.00 Special Servicing Fee 0.00 0.00 Pass-Through Rate 5.792181 5.091739

~~Pursuant~~Miscellaneous toReporting ~~the~~Group ~~requirements~~G1 of30Y ~~the~~Jumbo ~~Securities~~A ~~Exchange~~Arm ~~Act~~Insurance ofProceeds ~~1934,~~0.00 ~~the~~Net ~~registrant~~Liquidation ~~duly~~Proceeds ~~caused~~0.00 ~~this~~Repurchase ~~report~~Principal to0.00 beSubsequent ~~signed~~Losses on0.00 ~~its~~Subsequent ~~behalf~~Loss byRecoveries ~~the~~0.00 ~~undersigned~~Substitution ~~hereunto~~Amount ~~duly~~0.00 ~~authorized~~Substitution Adjustment Amount 0.00 Group G2 30Y Jumbo A Arm Insurance Proceeds 0.00 Net Liquidation Proceeds 0.00 Repurchase Principal 0.00 Subsequent Losses 0.00 Subsequent Loss Recoveries 0.00 Substitution Amount 0.00 Substitution Adjustment Amount 0.00 Group G3 30Y Jumbo A Arm Insurance Proceeds 0.00 Net Liquidation Proceeds 0.00 Repurchase Principal 0.00 Subsequent Losses 0.00 Subsequent Loss Recoveries 0.00 Substitution Amount 0.00 Substitution Adjustment Amount 0.00

~~CREDIT~~Miscellaneous ~~SUISSE~~Reporting ~~FIRST~~Group ~~BOSTON~~G4 30Y Jumbo A Arm Insurance Proceeds 0.00 Net Liquidation Proceeds 0.00 Repurchase Principal 0.00 Subsequent Losses 0.00 Subsequent Loss Recoveries 0.00 Substitution Amount 0.00 Substitution Adjustment Amount 0.00 Group G5 30Y Jumbo A Arm Insurance Proceeds 0.00 Net Liquidation Proceeds 0.00 Repurchase Principal 0.00 Subsequent Losses 0.00 Subsequent Loss Recoveries 0.00 Substitution Amount 0.00 Substitution Adjustment Amount 0.00 Group G6A 30Y Alt A Arm Insurance Proceeds 0.00 Net Liquidation Proceeds 0.00 Repurchase Principal 0.00 Subsequent Losses 0.00 Subsequent Loss Recoveries 0.00 Substitution Amount 0.00 Substitution Adjustment Amount 0.00

~~MORTGAGE~~Miscellaneous ~~SECURITIES~~Reporting ~~CORP~~Group G6B 30Y Alt A Arm Insurance Proceeds 0.00 Net Liquidation Proceeds 0.00 Repurchase Principal 0.00 Subsequent Losses 0.00 Subsequent Loss Recoveries 0.00 Substitution Amount 0.00 Substitution Adjustment Amount 0.00

By: /s/ John P. Graham

Name: John P. Graham

Title:

Vice President

Dated: October 22, 2004

Exhibit Index

Exhibit

Page

8.1

Tax Opinion of McKee Nelson LLP

Exhibit 8.1

MCKEE NELSON LLP

5 Times Square, 35th Floor

New York, New York 10036

Telephone: (917) 777-4200

Facsimile: (917) 777-4299

July 29, 2004

Credit Suisse First Boston LLC 11 Madison Avenue New York, New York 10010

U.S. Bank National Association

Corporate Trust Services – EP-MN-WS3D

60 Livingston Avenue

St. Paul, Minnesota 55107-2292

Moody’s Investors Service, Inc. 99 Church Street New York, New York 10007

Standard & Poor’s Ratings Services, a division of The McGraw-Hill Companies, Inc. 55 Water Street New York, New York 10041

Re:

Credit Suisse First Boston Mortgage Securities Corp.,

CSFB Mortgage-Backed Pass-Through Certificates, Series 2004-AR7

Ladies and Gentlemen:

We have acted as special counsel for Credit Suisse First Boston Mortgage Securities Corp., a Delaware corporation (the “Company”), in connection with the issuance of the CSFB Mortgage-Backed Pass-Through Certificates of the above-referenced Series (the “Certificates”). The Class 1-A-1, Class 2-A-1, Class 3-A-1, Class 4-A-1, Class 5-A-1, Class 6-A-1, Class 6-A-2, Class 6-A-3, Class 6-A-4, Class 6-A-5, Class 6-M-1, Class 6-M-2, Class 6-M-3, Class 6-M-4, Class C-B-1, Class C-B-2, Class C-B-3, Class C-B-1X, Class C-B-4, Class C-B-5 and Class C-B-6 Certificates are referred to herein as the “Regular Interest Certificates.”

The Certificates will represent the entire beneficial ownership interest in a trust fund (the “Trust Fund”) to be created pursuant to a Pooling and Servicing Agreement dated as of July 1, 2004 (the “Pooling Agreement”), among the Company, as depositor (the “Depositor”), U.S. Bank National Association, as trustee (the “Trustee”), DLJ Mortgage Capital, Inc., as a seller (“DLJMC”), Washington Mutual Mortgage Securities Corp., as a seller and a servicer (“WMMSC”), Wells Fargo Bank, N.A., as master servicer, as a servicer and as trust administrator (“Wells Fargo”), GreenPoint Mortgage Funding, Inc., as a servicer (“GreenPoint”), Select Portfolio Servicing, Inc., as a servicer (“SLS”) and Wilshire Credit Corporation, as special servicer (“Wilshire” and together with WMMSC, Wells Fargo, GreenPoint and SLS, the “Servicers”). The assets of the Trust Fund will consist primarily of (i) a pool of conventional adjustable-rate mortgage loans (the “Mortgage Loans”) secured by first liens on one- to four-family residential properties and (ii) the amounts on deposit in the Prefunding Account and Capitalized Interest Account. Capitalized terms not otherwise defined herein have the meanings ascribed to such terms in the Pooling Agreement.

In arriving at the opinions expressed below, we have examined such documents and records as we have deemed appropriate, including the following:

(1)

A signed copy of the Registration Statement on Form S-3 (File No. 333-115435) filed by the Company with the Securities and Exchange Commission (the “Commission”) under the Securities Act of 1933, as amended (the “1933 Act”), on May 13, 2004, together with each amendment thereto (such registration statement, as amended and as declared effective by the Commission on June 7, 2004, is referred to herein as the “Registration Statement”).

(2)

The Prospectus dated June 25, 2004 (the “Base Prospectus”), as supplemented by the Prospectus Supplement, dated July 28, 2004 (the “Prospectus Supplement”), in the form to be filed with the Commission pursuant to Rule 424(b) under the 1933 Act (the Base Prospectus, as supplemented by the Prospectus Supplement, the “Prospectus”).

(3)

The Pooling Agreement (together with the Prospectus, the “Documents”).

(4)

A specimen Certificate of each Class of Certificates.

In addition, we have made such investigations of such matters of law as we deemed appropriate as a basis for the opinions expressed below. Further, we have assumed the genuineness of all signatures and the authenticity of all documents submitted to us as originals. Our opinions are also based on the assumption that there are no agreements or understandings with respect to those transactions contemplated in the Documents other than those contained in the Documents. Furthermore, our opinions are based on the assumption that all parties to the Documents will comply with the terms thereof, including all tax reporting requirements contained therein.

As to any facts material to the following opinions which we did not independently establish or verify, we have relied upon statements and representations of the responsible officers and other representatives of the Company and of public officials and agencies. We have, for purposes of rendering the opinions, also relied on certain factual, numerical and statistical information which is based on the assumptions used in pricing the Certificates.

Based upon the foregoing and assuming compliance with the Pooling Agreement and compliance with changes in the law, including any amendments to the Internal Revenue Code of 1986, as amended (the “Code”) or applicable Treasury regulations thereunder, we are of the opinion that, as of the Closing Date: (i) each REMIC created pursuant to the Pooling Agreement will qualify as a REMIC within the meaning of Section 860D of the Code; (ii) the Regular Interest Certificates represent ownership of regular interests in the Master REMIC; (iii) the Class AR-L Certificates represent ownership of the residual interests in the Subsidiary REMICs and the Class AR Certificates represent ownership of the residual interest in each remaining REMIC created pursuant to the Pooling Agreement; and (iv) the rights of the Class 6-A-1, Class 6-A-2, Class 6-A-3, Class 6-A-4, Class 6-A-5, Class 6-M-1, Class 6-M-2, Class 6-M-3 and Class 6-M-4 Certificates to receive Basis Risk Shortfall represents separate contractual rights coupled with the REMIC regular interest represented by such Class within the meaning of Treasury Regulation Section 1.860G-2(i).

In addition, based upon the foregoing, it is our opinion that, under existing laws of the State of New York and the City of New York, insofar as each REMIC qualifies as a REMIC under Section 860D(a) of the Code: (i) each REMIC will be exempt from all taxes imposed or authorized by New York State upon its capital stock, franchises or income, and (ii) each REMIC will be exempt from taxes imposed by chapter five of the New York City tax law (the New York City Unincorporated Business Income Tax) and taxes imposed by chapter six of the New York City tax law (the New York City Business Tax).

The statements in the Base Prospectus and the Prospectus Supplement, as the case may be, under the heading “Material Federal Income Tax Consequences,” and “Federal Income Tax Consequences,” respectively, to the extent that they constitute matters of federal law or legal conclusions with respect thereto, have been reviewed by us and are correct in all material respects.

The opinions set forth herein are based upon the existing provisions of the Code and Treasury regulations issued or proposed thereunder, published Revenue Rulings and releases of the Internal Revenue Service and existing case law, the tax law of the State of New York, Chapters Five and Six of the New York City tax law and any regulations issued or proposed thereunder and releases of the New York Department of Finance and Taxation and the New York City Finance Administration, any of which could be changed at any time. Any such changes may be retroactive in application and could modify the legal conclusions upon which such opinions are based. The opinions expressed herein are limited as described above, and we do not express an opinion on any other tax aspect of the transactions contemplated by the documents relating to the transaction.

In rendering the foregoing opinions, we express no opinion as to the laws of any jurisdiction other than the federal income tax laws of the United States or the tax laws of the State or City of New York. This opinion is rendered as of the date hereof and we undertake no obligation to update this opinion or advise you of any changes in the event there is any change in legal authorities, facts, assumptions or documents on which this opinion is based (including the taking of any action by any party to the Documents pursuant to any opinion of counsel or a waiver), or any inaccuracy in any of the representations, warranties or assumptions upon which we have relied in rendering this opinion unless we are specifically engaged to do so. This opinion is rendered only to those to whom it is addressed and may not be relied on in connection with any transactions other than the transactions contemplated herein. This opinion may not be relied upon for any other purpose, or relied upon by any other person, firm or corporation for any purpose, without our prior written consent.

Very truly yours,

/s/ McKee Nelson LLP

McKee Nelson LLP

MCKEE NELSON LLP

5 Times Square, 35th Floor

New York, New York 10036

Telephone: (917) 777-4200

Facsimile: (917) 777-4299

October 22, 2004

BY MODEM

Securities and Exchange Commission

Judiciary Plaza

450 Fifth Street, N.W.

Washington, D.C. 20549

RE:

Credit Suisse First Boston Mortgage Securities Corp.,

Mortgage-Backed Pass-Through Certificates, Series 2004-AR8

Ladies and Gentlemen:

We have acted as counsel for Credit Suisse First Boston Mortgage Securities Corp., a Delaware corporation (the “Company”). We enclose herewith for filing, pursuant to the Securities and Exchange Act of 1934, as amended, the Company’s Current Report on Form 8-K in connection with the above-referenced transaction.

Very truly yours,

/s/ Michael Braun___

Michael Braun

Enclosure

Filing Compare · CSFB MORTGAGE-BACKED PASS-THROUGH CERTIFICATES, SERIES 2004-AR7