8-K 1 mab05op1_10506.txt 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): June 27, 2005 MASTR ASSET BACKED SECURITIES TRUST Mortgage Pass-Through Certificates, Series 2005-OP1 Trust (Exact name of registrant as specified in its charter) New York (governing law of 333-106982-69 Pooling and Servicing Agreement) (Commission 54-2175560 (State or other File Number) 54-2175561 jurisdiction 54-2175562 of Incorporation) 54-2175563 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 June 27, 2005 a distribution was made to holders of MASTR ASSET BACKED SECURITIES TRUST, Mortgage Pass-Through Certificates, Series 2005-OP1 Trust. ITEM 9.01 Financial Statements and Exhibits (c) Exhibits Exhibit Number Description EX-99.1 Monthly report distributed to holders of Mortgage Pass-Through Certificates, Series 2005-OP1 Trust, relating to the June 27, 2005 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. MASTR ASSET BACKED SECURITIES TRUST Mortgage Pass-Through Certificates, Series 2005-OP1 Trust (Registrant) By: Wells Fargo Bank, N.A. as Trustee By: /s/ Beth Belfield as Officer By: Beth Belfield as Officer Date: 6/30/2005 INDEX TO EXHIBITS Exhibit Number Description EX-99.1 Monthly report distributed to holders of Mortgage Pass-Through Certificates, Series 2005-OP1 Trust, relating to the June 27, 2005 distribution. EX-99.1

~~SECURITIES~~MASTR ~~AND~~Asset ~~EXCHANGE~~Backed ~~COMMISSION~~Securities Mortgage Pass-Through Certificates Record Date: 5/31/2005 Distribution Date: 6/27/2005 MASTR Asset Backed Securities Mortgage Pass-Through Certificates Series 2005-OP1 Contact: Customer Service - CTSLink Wells Fargo Bank, N.A. Securities Administration Services 7485 New Horizon Way Frederick, MD 21703 www.ctslink.com Telephone: (301) 815-6600 Fax: (301) 815-6660 Certificateholder Distribution Summary Certificate Certificate Beginning Class Pass-Through Certificate Interest Class CUSIP Description Rate Balance Distribution A-1 57643LHJ8 SEN 3.39500% 666,810,000.00 2,892,658.83 A-2 57643LHK5 SEN 3.35000% 74,091,000.00 317,150.64 A-3 57643LHL3 SEN 3.18000% 316,612,000.00 1,286,500.09 A-4 57643LHM1 SEN 3.27000% 247,690,000.00 1,034,931.38 A-5 57643LHN9 SEN 3.40000% 45,612,000.00 198,158.80 M-1 57643LHP4 MEZ 3.49000% 46,469,000.00 207,225.92 M-2 57643LHQ2 MEZ 3.51000% 37,656,000.00 168,887.16 M-3 57643LHR0 MEZ 3.55000% 24,837,000.00 112,663.39 M-4 57643LHS8 MEZ 3.59000% 39,259,000.00 180,089.76 M-5 57643LHT6 MEZ 3.69000% 13,620,000.00 64,218.30 M-6 57643LHU3 MEZ 3.77000% 15,223,000.00 73,332.57 M-7 57643LHV1 MEZ 4.01000% 18,427,000.00 94,417.90 M-8 57643LHW9 MEZ 4.09000% 14,422,000.00 75,370.97 M-9 57643LHX7 MEZ 4.84000% 15,223,000.00 94,145.80 M-10 57643LHY5 MEZ 5.59000% 8,012,000.00 57,227.94 M-11 57643LHZ2 MEZ 6.59000% 7,211,000.00 60,720.63 CE MAB5OPT1C OC 0.00000% 11,215,935.00 1,211,509.35 P MAB5OPT1P RES 0.00000% 100.00 651,292.83 Totals 1,602,390,035.00 8,780,502.26

~~WASHINGTON~~Certificateholder Distribution Summary (continued) Current Ending Cumulative Principal Realized Certificate Total Realized Class Distribution Loss Balance Distribution Losses A-1 24,931,818.34 D0.C00 641,878,181.66 ~~20549~~27,824,477.17 0.00 A-2 2,770,239.43 0.00 71,320,760.57 3,087,390.07 0.00 A-3 20,453,547.03 0.00 296,158,452.97 21,740,047.12 0.00 A-4 0.00 0.00 247,690,000.00 1,034,931.38 0.00 A-5 0.00 0.00 45,612,000.00 198,158.80 0.00 M-1 0.00 0.00 46,469,000.00 207,225.92 0.00 M-2 0.00 0.00 37,656,000.00 168,887.16 0.00 M-3 0.00 0.00 24,837,000.00 112,663.39 0.00 M-4 0.00 0.00 39,259,000.00 180,089.76 0.00 M-5 0.00 0.00 13,620,000.00 64,218.30 0.00 M-6 0.00 0.00 15,223,000.00 73,332.57 0.00 M-7 0.00 0.00 18,427,000.00 94,417.90 0.00 M-8 0.00 0.00 14,422,000.00 75,370.97 0.00 M-9 0.00 0.00 15,223,000.00 94,145.80 0.00 M-10 0.00 0.00 8,012,000.00 57,227.94 0.00 M-11 0.00 0.00 7,211,000.00 60,720.63 0.00 CE 0.00 0.00 11,216,730.25 1,211,509.35 0.00 P 0.00 0.00 100.00 651,292.83 0.00 Totals 48,155,604.80 0.00 1,554,235,225.45 56,936,107.06 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) A-1 666,810,000.00 666,810,000.00 0.00 24,931,818.34 0.00 0.00 A-2 74,091,000.00 74,091,000.00 0.00 2,770,239.43 0.00 0.00 A-3 316,612,000.00 316,612,000.00 0.00 20,453,547.03 0.00 0.00 A-4 247,690,000.00 247,690,000.00 0.00 0.00 0.00 0.00 A-5 45,612,000.00 45,612,000.00 0.00 0.00 0.00 0.00 M-1 46,469,000.00 46,469,000.00 0.00 0.00 0.00 0.00 M-2 37,656,000.00 37,656,000.00 0.00 0.00 0.00 0.00 M-3 24,837,000.00 24,837,000.00 0.00 0.00 0.00 0.00 M-4 39,259,000.00 39,259,000.00 0.00 0.00 0.00 0.00 M-5 13,620,000.00 13,620,000.00 0.00 0.00 0.00 0.00 M-6 15,223,000.00 15,223,000.00 0.00 0.00 0.00 0.00 M-7 18,427,000.00 18,427,000.00 0.00 0.00 0.00 0.00 M-8 14,422,000.00 14,422,000.00 0.00 0.00 0.00 0.00 M-K9 15,223,000.00 15,223,000.00 0.00 0.00 0.00 0.00 M-10 8,012,000.00 8,012,000.00 0.00 0.00 0.00 0.00 M-11 7,211,000.00 7,211,000.00 0.00 0.00 0.00 0.00 CE 11,215,935.00 11,215,935.00 0.00 0.00 0.00 0.00 P 100.00 100.00 0.00 0.00 0.00 0.00 Totals 1,602,390,035.00 1,602,390,035.00 0.00 48,155,604.80 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 A-1 24,931,818.34 641,878,181.66 0.96261031 24,931,818.34 A-2 2,770,239.43 71,320,760.57 0.96261031 2,770,239.43 A-3 20,453,547.03 296,158,452.97 0.93539870 20,453,547.03 A-4 0.00 247,690,000.00 1.00000000 0.00 A-5 0.00 45,612,000.00 1.00000000 0.00 M-1 0.00 46,469,000.00 1.00000000 0.00 M-2 0.00 37,656,000.00 1.00000000 0.00 M-3 0.00 24,837,000.00 1.00000000 0.00 M-4 0.00 39,259,000.00 1.00000000 0.00 M-5 0.00 13,620,000.00 1.00000000 0.00 M-6 0.00 15,223,000.00 1.00000000 0.00 M-7 0.00 18,427,000.00 1.00000000 0.00 M-8 0.00 14,422,000.00 1.00000000 0.00 M-9 0.00 15,223,000.00 1.00000000 0.00 M-10 0.00 8,012,000.00 1.00000000 0.00 M-11 0.00 7,211,000.00 1.00000000 0.00 CE 0.00 11,216,730.25 1.00007090 0.00 P 0.00 100.00 1.00000000 0.00 Totals 48,155,604.80 1,554,235,225.45 0.96994813 48,155,604.80

~~Pursuant~~Principal toDistribution ~~Section~~Factors Statement Original Beginning Scheduled Unscheduled Face Certificate Principal Principal Class (2) Amount Balance Distribution Distribution Accretion A-1 666,810,000.00 1000.00000000 0.00000000 37.38968873 0.00000000 A-2 74,091,000.00 1000.00000000 0.00000000 37.38968876 0.00000000 A-3 316,612,000.00 1000.00000000 0.00000000 64.60130074 0.00000000 A-4 247,690,000.00 1000.00000000 0.00000000 0.00000000 0.00000000 A-5 45,612,000.00 1000.00000000 0.00000000 0.00000000 0.00000000 M-1 46,469,000.00 1000.00000000 0.00000000 0.00000000 0.00000000 M-2 37,656,000.00 1000.00000000 0.00000000 0.00000000 0.00000000 M-3 24,837,000.00 1000.00000000 0.00000000 0.00000000 0.00000000 M-4 39,259,000.00 1000.00000000 0.00000000 0.00000000 0.00000000 M-5 13,620,000.00 or1000.00000000 0.00000000 0.00000000 0.00000000 M-6 15,223,000.00 1000.00000000 0.00000000 0.00000000 0.00000000 M-7 18,427,000.00 1000.00000000 0.00000000 0.00000000 0.00000000 M-8 14,422,000.00 1000.00000000 0.00000000 0.00000000 0.00000000 M-9 15,223,000.00 1000.00000000 0.00000000 0.00000000 0.00000000 M-10 8,012,000.00 1000.00000000 0.00000000 0.00000000 0.00000000 M-11 7,211,000.00 1000.00000000 0.00000000 0.00000000 0.00000000 CE 11,215,935.00 1000.00000000 0.00000000 0.00000000 0.00000000 P 100.00 1000.00000000 0.00000000 0.00000000 0.00000000 (d2) ofAll ~~the~~amounts are per 1,000 dollar denomination.

~~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 A-1 0.00000000 37.38968873 962.61031127 0.96261031 37.38968873 A-2 0.00000000 37.38968876 962.61031124 0.96261031 37.38968876 A-3 0.00000000 64.60130074 935.39869926 0.93539870 64.60130074 A-4 0.00000000 0.00000000 1,000.00000000 1.00000000 0.00000000 A-5 0.00000000 0.00000000 1,000.00000000 1.00000000 0.00000000 M-1 0.00000000 0.00000000 1,000.00000000 1.00000000 0.00000000 M-2 0.00000000 0.00000000 1,000.00000000 1.00000000 0.00000000 M-3 0.00000000 0.00000000 1,000.00000000 1.00000000 0.00000000 M-4 0.00000000 0.00000000 1,000.00000000 1.00000000 0.00000000 M-5 0.00000000 0.00000000 1,000.00000000 1.00000000 0.00000000 M-6 0.00000000 0.00000000 1,000.00000000 1.00000000 0.00000000 M-7 0.00000000 0.00000000 1,000.00000000 1.00000000 0.00000000 M-8 0.00000000 0.00000000 1,000.00000000 1.00000000 0.00000000 M-9 0.00000000 0.00000000 1,000.00000000 1.00000000 0.00000000 M-10 0.00000000 0.00000000 1,000.00000000 1.00000000 0.00000000 M-11 0.00000000 0.00000000 1,000.00000000 1.00000000 0.00000000 CE 0.00000000 0.00000000 1,000.07090358 1.00007090 0.00000000 P 0.00000000 0.00000000 1,000.00000000 1.00000000 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 ~~reported):~~Certificate/ ~~May~~Current 12Unpaid Current Face Certificate Notional Accrued Interest Interest Class Amount Rate Balance Interest Shortfall Shortfall A-1 666,810,000.00 ~~2005~~3.39500% 666,810,000.00 2,892,658.83 0.00 0.00 A-2 74,091,000.00 3.35000% 74,091,000.00 317,150.64 0.00 0.00 A-3 316,612,000.00 3.18000% 316,612,000.00 1,286,500.09 0.00 0.00 A-4 247,690,000.00 3.27000% 247,690,000.00 1,034,931.38 0.00 0.00 A-5 45,612,000.00 3.40000% 45,612,000.00 198,158.80 0.00 0.00 M-1 46,469,000.00 3.49000% 46,469,000.00 207,225.92 0.00 0.00 M-2 37,656,000.00 3.51000% 37,656,000.00 168,887.16 0.00 0.00 M-3 24,837,000.00 3.55000% 24,837,000.00 112,663.39 0.00 0.00 M-4 39,259,000.00 3.59000% 39,259,000.00 180,089.76 0.00 0.00 M-5 13,620,000.00 3.69000% 13,620,000.00 64,218.30 0.00 0.00 M-6 15,223,000.00 3.77000% 15,223,000.00 73,332.57 0.00 0.00 M-7 18,427,000.00 4.01000% 18,427,000.00 94,417.90 0.00 0.00 M-8 14,422,000.00 4.09000% 14,422,000.00 75,370.97 0.00 0.00 M-9 15,223,000.00 4.84000% 15,223,000.00 94,145.80 0.00 0.00 M-10 8,012,000.00 5.59000% 8,012,000.00 57,227.94 0.00 0.00 M-11 7,211,000.00 6.59000% 7,211,000.00 60,720.63 0.00 0.00 CE 11,215,935.00 0.00000% 11,215,935.00 0.00 0.00 0.00 P 100.00 0.00000% 100.00 0.00 0.00 0.00 Totals 1,602,390,035.00 6,917,700.08 0.00 0.00

~~MORTGAGE~~Interest ~~ASSET~~Distribution ~~SECURITIZATION~~Statement ~~TRANSACTIONS~~(continued) Remaining Ending Non-Supported Total Unpaid Certificate/ Interest Realized Interest Interest Notional Class Shortfall Losses (4) Distribution Shortfall Balance A-1 0.00 0.00 2,892,658.83 ~~INC~~0.00 641,878,181.66 A-2 0.00 0.00 317,150.64 0.00 71,320,760.57 A-3 0.00 0.00 1,286,500.09 0.00 296,158,452.97 A-4 0.00 0.00 1,034,931.38 0.00 247,690,000.00 A-5 0.00 0.00 198,158.80 0.00 45,612,000.00 M-1 0.00 0.00 207,225.92 0.00 46,469,000.00 M-2 0.00 0.00 168,887.16 0.00 37,656,000.00 M-3 0.00 0.00 112,663.39 0.00 24,837,000.00 M-4 0.00 0.00 180,089.76 0.00 39,259,000.00 M-5 0.00 0.00 64,218.30 0.00 13,620,000.00 M-6 0.00 0.00 73,332.57 0.00 15,223,000.00 M-7 0.00 0.00 94,417.90 0.00 18,427,000.00 M-8 0.00 0.00 75,370.97 0.00 14,422,000.00 M-9 0.00 0.00 94,145.80 0.00 15,223,000.00 M-10 0.00 0.00 57,227.94 0.00 8,012,000.00 M-11 0.00 0.00 60,720.63 0.00 7,211,000.00 CE 0.00 0.00 1,211,509.35 0.00 11,216,730.25 P 0.00 0.00 651,292.83 0.00 100.00 Totals 0.00 0.00 8,780,502.26 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.

Interest Distribution Factors Statement Beginning Payment of Original Current Certificate/ Current Unpaid Current Face Certificate Notional Accrued Interest Interest Class (as5) ~~depositor~~Amount ~~under~~Rate ~~the~~Balance ~~Pooling~~Interest ~~and~~Shortfall ~~Servicing~~Shortfall ~~Agreement~~A-1 666,810,000.00 3.39500% 1000.00000000 4.33805556 0.00000000 0.00000000 A-2 74,091,000.00 3.35000% 1000.00000000 4.28055553 0.00000000 0.00000000 A-3 316,612,000.00 3.18000% 1000.00000000 4.06333332 0.00000000 0.00000000 A-4 247,690,000.00 3.27000% 1000.00000000 4.17833332 0.00000000 0.00000000 A-5 45,612,000.00 3.40000% 1000.00000000 4.34444444 0.00000000 0.00000000 M-1 46,469,000.00 3.49000% 1000.00000000 4.45944436 0.00000000 0.00000000 M-2 37,656,000.00 3.51000% 1000.00000000 4.48500000 0.00000000 0.00000000 M-3 24,837,000.00 3.55000% 1000.00000000 4.53611104 0.00000000 0.00000000 M-4 39,259,000.00 3.59000% 1000.00000000 4.58722229 0.00000000 0.00000000 M-5 13,620,000.00 3.69000% 1000.00000000 4.71500000 0.00000000 0.00000000 M-6 15,223,000.00 3.77000% 1000.00000000 4.81722197 0.00000000 0.00000000 M-7 18,427,000.00 4.01000% 1000.00000000 5.12388886 0.00000000 0.00000000 M-8 14,422,000.00 4.09000% 1000.00000000 5.22611080 0.00000000 0.00000000 M-9 15,223,000.00 4.84000% 1000.00000000 6.18444459 0.00000000 0.00000000 M-10 8,012,000.00 5.59000% 1000.00000000 7.14277833 0.00000000 0.00000000 M-11 7,211,000.00 6.59000% 1000.00000000 8.42055609 0.00000000 0.00000000 CE 11,215,935.00 0.00000% 1000.00000000 0.00000000 0.00000000 0.00000000 P 100.00 0.00000% 1000.00000000 0.00000000 0.00000000 0.00000000 (2) All amounts are per 1,000 dollar denomination.

~~dated~~Interest asDistribution ofFactors ~~May~~Statement (continued) Remaining Ending Non-Supported Total Unpaid Certificate/ Interest Realized Interest Interest Notional Class Shortfall Losses (6) Distribution Shortfall Balance A-1 0.00000000 0.00000000 4.33805556 0.00000000 962.61031127 A-2 0.00000000 0.00000000 4.28055553 0.00000000 962.61031124 A-3 0.00000000 0.00000000 4.06333332 0.00000000 935.39869926 A-4 0.00000000 0.00000000 4.17833332 0.00000000 1000.00000000 A-5 0.00000000 0.00000000 4.34444444 0.00000000 1000.00000000 M-1 0.00000000 0.00000000 4.45944436 0.00000000 1000.00000000 M-2 0.00000000 0.00000000 4.48500000 0.00000000 1000.00000000 M-3 0.00000000 0.00000000 4.53611104 0.00000000 1000.00000000 M-4 0.00000000 0.00000000 4.58722229 0.00000000 1000.00000000 M-5 0.00000000 0.00000000 4.71500000 0.00000000 1000.00000000 M-6 0.00000000 0.00000000 4.81722197 0.00000000 1000.00000000 M-7 0.00000000 0.00000000 5.12388886 0.00000000 1000.00000000 M-8 0.00000000 0.00000000 5.22611080 0.00000000 1000.00000000 M-9 0.00000000 0.00000000 6.18444459 0.00000000 1000.00000000 M-10 0.00000000 0.00000000 7.14277833 0.00000000 1000.00000000 M-11 0.00000000 0.00000000 8.42055609 0.00000000 1000.00000000 CE 0.00000000 0.00000000 108.01679485 0.00000000 1000.07090358 P 0.00000000 0.00000000 6512928.30000000 0.00000000 1000.00000000 (6) Amount Does Not Include Excess Special Hazard, ~~2005~~Bankruptcy,or ~~providing~~Fraud ~~for~~Losses Unless Otherwise Disclosed. Please Refer to the ~~issuance~~Prospectus ofSupplement for a Full Description.

~~Mortgage~~CERTIFICATEHOLDER ~~Pass-Through~~ACCOUNT ~~Certificates~~STATEMENT CERTIFICATE ACCOUNT Beginning Balance 0.00 Deposits Payments of Interest and Principal 57,596,851.33 ~~Series~~Liquidations, ~~2005-OPT1~~Insurance Proceeds, Reserve Funds 0.00 Proceeds from Repurchased Loans 0.00 Other Amounts (Servicer Advances) 0.00 Realized Loss (Gains, Subsequent Expenses & Recoveries) 0.00 Prepayment Penalties 651,292.83 Total Deposits 58,248,144.16 Withdrawals Reimbursement for Servicer Advances 0.00 Payment of Service Fee 1,312,037.10 Payment of Interest and Principal 56,936,107.06 Total Withdrawals (Pool Distribution Amount) 58,248,144.16 Ending Balance 0.00

~~Mortgage~~PREPAYMENT/CURTAILMENT ~~Asset~~INTEREST ~~Securitization~~SHORTFALL ~~Transactions,~~Total ~~Inc~~Prepayment/Curtailment Interest Shortfall 0.00 Servicing Fee Support 0.00 Non-Supported Prepayment/Curtailment Interest Shortfall 0.00

~~(Exact~~SERVICING ~~name~~FEES ofGross ~~registrant~~Servicing asFee ~~specified~~400,597.51 inMGIC ~~its~~526,736.62 ~~charter)~~Radian 380,029.33 Wells Fargo Bank, N.A. 4,673.64 Supported Prepayment/Curtailment Interest Shortfall 0.00 Net Servicing Fee 1,312,037.10

~~_____________________________________________________________________________~~OTHER ACCOUNTS Beginning Current Current Ending Account Type Balance Withdrawals Deposits Balance Reserve Fund 0.00 0.00 0.00 0.00

Delaware	333-106982	06-1204982
(State or Other Jurisdiction of Incorporation)	(Commission File Number)	(I.R.S. Employer Identification Number)
1285 Avenue of the Americas New York, New York	10019
Registrant’s telephone number, including area code: (212) 713-2000

Delinquency Status By Groups

DELINQUENT BANKRUPTCY FORECLOSURE REO Total 1 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 3 0 0 3 340,579.60 0.00 0.00 340,579.60 30 Days 0 0 0 0 0 0.00 0.00 0.00 0.00 0.00 60 Days 0 0 0 0 0 0.00 0.00 0.00 0.00 0.00 90 Days 0 0 0 0 0 0.00 0.00 0.00 0.00 0.00 120 Days 0 0 0 0 0 0.00 0.00 0.00 0.00 0.00 150 Days 0 0 0 0 0 0.00 0.00 0.00 0.00 0.00 180+ Days 0 0 0 0 0 0.00 0.00 0.00 0.00 0.00 Totals 0 3 0 0 3 0.00 340,579.60 0.00 0.00 340,579.60 0-29 Days 0.306435% 0.000000% 0.000000% 0.306435% 0.229761% 0.000000% 0.000000% 0.229761% 30 Days 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 60 Days 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 90 Days 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 120 Days 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 150 Days 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 180+ Days 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% Totals 0.000000% 0.306435% 0.000000% 0.000000% 0.306435% 0.000000% 0.229761% 0.000000% 0.000000% 0.229761% DELINQUENT BANKRUPTCY FORECLOSURE REO Total 2 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 9 0 0 9 973,388.11 0.00 0.00 973,388.11 30 Days 2 0 0 0 2 196,488.26 0.00 0.00 0.00 196,488.26 60 Days 0 0 0 0 0 0.00 0.00 0.00 0.00 0.00 90 Days 0 0 0 0 0 0.00 0.00 0.00 0.00 0.00 120 Days 0 0 0 0 0 0.00 0.00 0.00 0.00 0.00 150 Days 0 0 0 0 0 0.00 0.00 0.00 0.00 0.00 180+ Days 0 0 0 0 0 0.00 0.00 0.00 0.00 0.00 Totals 2 9 0 0 11 196,488.26 973,388.11 0.00 0.00 1,169,876.37 0-29 Days 0.218500% 0.000000% 0.000000% 0.218500% 0.138438% 0.000000% 0.000000% 0.138438% 30 Days 0.048555% 0.000000% 0.000000% 0.000000% 0.048555% 0.027945% 0.000000% 0.000000% 0.000000% 0.027945% 60 Days 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 90 Days 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 120 Days 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 150 Days 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 180+ Days 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% Totals 0.048555% 0.218500% 0.000000% 0.000000% 0.267055% 0.027945% 0.138438% 0.000000% 0.000000% 0.166383% DELINQUENT BANKRUPTCY FORECLOSURE REO Total 3 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 3 0 0 3 246,262.26 0.00 0.00 246,262.26 30 Days 0 0 0 0 0 0.00 0.00 0.00 0.00 0.00 60 Days 0 0 0 0 0 0.00 0.00 0.00 0.00 0.00 90 Days 0 0 0 0 0 0.00 0.00 0.00 0.00 0.00 120 Days 0 0 0 0 0 0.00 0.00 0.00 0.00 0.00 150 Days 0 0 0 0 0 0.00 0.00 0.00 0.00 0.00 180+ Days 0 0 0 0 0 0.00 0.00 0.00 0.00 0.00 Totals 0 3 0 0 3 0.00 246,262.26 0.00 0.00 246,262.26 0-29 Days 0.528169% 0.000000% 0.000000% 0.528169% 0.262944% 0.000000% 0.000000% 0.262944% 30 Days 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 60 Days 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 90 Days 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 120 Days 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 150 Days 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 180+ Days 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% Totals 0.000000% 0.528169% 0.000000% 0.000000% 0.528169% 0.000000% 0.262944% 0.000000% 0.000000% 0.262944% DELINQUENT BANKRUPTCY FORECLOSURE REO Total 4 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 2 0 0 2 463,425.14 0.00 0.00 463,425.14 30 Days 1 0 0 0 1 92,719.30 0.00 0.00 0.00 92,719.30 60 Days 0 0 0 0 0 0.00 0.00 0.00 0.00 0.00 90 Days 0 0 0 0 0 0.00 0.00 0.00 0.00 0.00 120 Days 0 0 0 0 0 0.00 0.00 0.00 0.00 0.00 150 Days 0 0 0 0 0 0.00 0.00 0.00 0.00 0.00 180+ Days 0 0 0 0 0 0.00 0.00 0.00 0.00 0.00 Totals 1 2 0 0 3 92,719.30 463,425.14 0.00 0.00 556,144.44 0-29 Days 0.071685% 0.000000% 0.000000% 0.071685% 0.076033% 0.000000% 0.000000% 0.076033% 30 Days 0.035842% 0.000000% 0.000000% 0.000000% 0.035842% 0.015212% 0.000000% 0.000000% 0.000000% 0.015212% 60 Days 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 90 Days 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 120 Days 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 150 Days 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 180+ Days 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% 0.000000% Totals 0.035842% 0.071685% 0.000000% 0.000000% 0.107527% 0.015212% 0.076033% 0.000000% 0.000000% 0.091245%

~~Check~~OTHER ~~the~~INFORMATION ~~appropriate~~Current ~~box~~Period ~~below~~Class ifA ~~the~~Insufficient ~~Form~~Funds ~~8-K~~0.00 ~~filing~~Principal isBalance ~~intended to simultaneously satisfy the filing obligation~~ of ~~the~~Contaminated ~~registrant~~Properties ~~under~~0.00 ~~any~~Periodic ofAdvance ~~the following provisions (see General Instruction A~~0.~~2. below):~~00

oSUBORDINATION ~~Written~~LEVEL/CREDIT ~~communications~~ENHANCEMENT/CLASS ~~pursuant~~PERCENTAGE toAND ~~Rule~~PREPAYMENT ~~425~~PERCENTAGE ~~under~~Current ~~the~~Original ~~Securities~~$ ~~Act~~Original ~~(17~~% ~~CFR~~Current ~~230~~$ Current % Class% Prepayment% Class M-1 205,106,035.~~425)~~00 12.80000690% 205,106,830.25 13.19664018% 2.989831% 0.000000% Class M-2 167,450,035.00 10.45001725% 167,450,830.25 10.77384089% 2.422799% 0.000000% Class M-3 142,613,035.00 8.90002009% 142,613,830.25 9.17582023% 1.598021% 0.000000% Class M-4 103,354,035.00 6.44999237% 103,354,830.25 6.64988340% 2.525937% 0.000000% Class CE 100.00 0.00000624% 100.00 0.00000643% 0.721688% 0.000000% Class P 0.00 0.00000000% 0.00 0.00000000% 0.000006% 0.000000% Please Refer to the Prospectus Supplement for a Full Description of Loss Exposure

oCOLLATERAL ~~Soliciting~~STATEMENT ~~material~~Collateral ~~pursuant~~Description toMixed ~~Rule~~Fixed ~~14a~~& Arm Weighted Average Gross Coupon 7.070969% Weighted Average Net Coupon 6.770969% Weighted Average Pass-12Through Rate 6.088408% Weighted Average Maturity(bStepdown Calculation) ~~under~~353 ~~the~~Beginning ~~Exchange~~Scheduled ~~Act~~Collateral ~~(17~~Loan ~~CFR~~Count ~~240~~8,683 Number Of Loans Paid In Full 227 Ending Scheduled Collateral Loan Count 8,456 Beginning Scheduled Collateral Balance 1,602,390,035.~~14a~~00 Ending Scheduled Collateral Balance 1,554,235,225.44 Ending Actual Collateral Balance at 31-~~12(b))~~May-2005 1,554,517,704.15 Monthly P&I Constant 10,535,706.13 Special Servicing Fee 0.00 Prepayment Penalties 651,292.83 Realized Loss Amount 0.00 Cumulative Realized Loss 0.00 Scheduled Principal 1,093,664.35 Unscheduled Principal 47,061,145.25

oMiscellaneous ~~Pre-commencement~~Reporting ~~communications~~Excess ~~pursuant~~Cash to1212304.555553% ~~Rule~~Extra ~~14d-2(b)~~Principal ~~under~~Distribution ~~the~~Amount ~~Exchange~~795.205278% ~~Act~~Overcollaterization ~~(17~~Amount ~~CFR~~11216730.245280% ~~240~~Overcollaterization Deficiency Amount 0.~~14d-2(b))~~000000% Overcollaterization Release Amount 0.000000% Overcollaterization Target Amount 11216730.245280% #SPEC_OC_AMT 11216730.245280% Stepdown Date 0.000000% Trigger Event in effect 0.000000%

oGroup ~~Pre-commencement~~Level ~~communications~~Collateral ~~pursuant~~Statement toGroup ~~Rule~~1 ~~13e-~~2 3 Collateral Description Fixed 15/30 & ARM Fixed 15/30 & ARM Fixed 15/30 & ARM Weighted Average Coupon Rate 7.282975 7.076518 7.237333 Weighted Average Net Rate 6.982975 6.776518 6.937333 Weighted Average Maturity 341 354 345 Beginning Loan Count 996 4~~(c)~~,243 ~~under~~576 ~~the~~Loans ~~Exchange~~Paid ~~Act~~In (Full 17 ~~CFR~~124 ~~240~~8 Ending Loan Count 979 4,119 568 Beginning Scheduled Balance 151,210,995.~~13e-~~70 727,675,203.81 94,845,588.95 Ending Scheduled Balance 148,207,273.66 702,977,325.53 93,640,520.19 Record Date 05/31/2005 05/31/2005 05/31/2005 Principal And Interest Constant 1,064,095.55 4~~(c))~~,816,653.89 653,710.43 Scheduled Principal 146,373.99 525,481.78 81,686.15 Unscheduled Principal 2,857,348.05 24,172,396.50 1,123,382.61 Scheduled Interest 917,721.56 4,291,172.11 572,024.28 Servicing Fees 37,802.75 181,918.80 23,711.40 Master Servicing Fees 0.00 0.00 0.00 Trustee Fee 441.03 2,122.39 276.63 FRY Amount 0.00 0.00 0.00 Special Hazard Fee 0.00 0.00 0.00 Other Fee 87,938.47 433,388.75 46,637.03 Pool Insurance Fee 0.00 0.00 0.00 Spread 1 0.00 0.00 0.00 Spread 2 0.00 0.00 0.00 Spread 3 0.00 0.00 0.00 Net Interest 791,539.31 3,673,742.17 501,399.22 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 6.281601 6.058322 6.343774

~~SECTION~~Group Level Collateral Statement Group 4 Total Collateral Description Fixed 15/30 & ARM Mixed Fixed & Arm Weighted Average Coupon Rate 6.988453 7.070969 Weighted Average Net Rate 6.688453 6.770969 Weighted Average Maturity 355 353 Beginning Loan Count 2-,868 ~~Completion~~8,683 ofLoans ~~Acquisition~~Paid ofIn ~~Disposition~~Full 78 227 Ending Loan Count 2,790 8,456 Beginning Scheduled Balance 628,658,246.58 1,602,390,035.04 Ending scheduled Balance 609,410,106.06 1,554,235,225.44 Record Date 05/31/2005 05/31/2005 Principal And Interest Constant 4,001,246.26 10,535,706.13 Scheduled Principal 340,122.43 1,093,664.35 Unscheduled Principal 18,908,018.09 47,061,145.25 Scheduled Interest 3,661,123.83 9,442,041.78 Servicing Fees 157,164.56 400,597.51 Master Servicing Fees 0.00 0.00 Trustee Fee 1,833.59 4,673.64 FRY Amount 0.00 0.00 Special Hazard Fee 0.00 0.00 Other Fee 338,801.70 906,765.95 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 3,163,323.98 8,130,004.68 Realized Loss Amount 0.00 0.00 Cumulative Realized Loss 0.00 0.00 Percentage of ~~Assets~~Cumulative Losses 0.0000 0.0000 Prepayment Penalties 651,292.83 651,292.83 Special Servicing Fee 0.00 0.00 Pass-Through Rate 6.038238 6.088408

Item 2.01 Acquisition or Disposition of Assets

Description of the Certificates and the Mortgage Pool

On May 12, 2005, a single series of certificates, entitled MASTR Asset Backed Securities Trust 2005-OPT1, Mortgage Pass-Through Certificates, Series 2005-OPT1 (the “Certificates”), were issued pursuant to a pooling and servicing agreement, dated as of May 1, 2005 (the “Agreement”), attached hereto as Exhibit 4.1, among Mortgage Asset Securitization Transactions, Inc. as depositor (the “Depositor”), Option One Mortgage Corporation as master servicer (the “Master Servicer”) and Wells Fargo Bank, N.A. as trustee (the “Trustee”). The Certificates consist of twenty classes of certificates (collectively, the “Certificates”), designated as the “Class A-1 Certificates”, “Class A-2 Certificates”, “Class A-3 Certificates”, “Class A-4 Certificates”, “Class A-5 Certificates”, “Class M-1 Certificates”, “Class M-2 Certificates”, “Class M-3 Certificates”, “Class M-4 Certificates”, “Class M-5 Certificates”, “Class M-6 Certificates”, “Class M-7 Certificates”, “Class M-8 Certificates”, “Class M-9 Certificates”, “Class M-10 Certificates”, “Class M-11 Certificates”, “Class CE Certificates”, “Class P Certificates”, “Class R Certificates” and “Class R-X Certificates”. The Certificates evidence in the aggregate the entire beneficial ownership interest in a trust fund (the “Trust Fund”), consisting of a pool of mortgage loans (the “Mortgage Pool’“) of conventional, one- to four- family, adjustable rate and fixed rate, first and second lien mortgage loans having original terms to maturity up to 30 years (the “Mortgage Loans”). The Mortgage Pool consists of Mortgage Loans having an aggregate principal balance of $1,602,390,035 as of May 1, 2005 (the “Cut-off Date”). The Mortgage Loans were purchased pursuant to the Mortgage Loan Purchase Agreement, dated May 10, 2005, among UBS Real Estate Securities Inc. (“UBSRES”), the Depositor and Option One Mortgage Corporation (the “Purchase Agreement”). The Class A-1 Certificates, the Class A-2 Certificates, the Class A-3 Certificates, the Class A-4 Certificates, the Class A-5 Certificates, the Class M-1 Certificates, the Class M-2 Certificates, the Class M-3 Certificates, the Class M-4 Certificates, the Class M-5 Certificates, the Class M-6 Certificates,

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the Class M-7 Certificates, the Class M-8 Certificates, the Class M-9 Certificates, the Class M-10 Certificates and the Class M-11 Certificates were sold by the Depositor to UBS Securities LLC (the “Underwriter”), pursuant to an Underwriting Agreement, dated May 10, 2005 (the “Underwriting Agreement”) between the Depositor and the Underwriter.

The Certificates have the following initial Certificate Balances and Pass-Through Rates:

Designation	Pass-Through Rate	Initial Aggregate Certificate Principal Balance
Class A-1	Variable	$666,810,000.00
Class A-2	Variable	$ 74,091,000.00
Class A-3	Variable	$316,612,000.00
Class A-4	Variable	$247,690,000.00
Class A-5	Variable	$ 45,612,000.00
Class M-1	Variable	$ 46,469,000.00
Class M-2	Variable	$ 37,656,000.00
Class M-3	Variable	$ 24,837,000.00
Class M-4	Variable	$ 39,259,000.00
Class M-5	Variable	$ 13,620,000.00
Class M-6	Variable	$ 15,223,000.00
Class M-7	Variable	$ 18,427,000.00
Class M-8	Variable	$ 14,422,000.00
Class M-9	Variable	$ 15,223,000.00
Class M-10	Variable	$ 8,012,000.00
Class M-11	Variable	$ 7,211,000.00
Class CE	Variable	$ 11,215,935.00
Class P	N/A	$ 100.00
Class R	N/A	100.00%
Class R-X	N/A	100.00%

The Certificates, other than the Class CE Certificates, the Class P Certificates and the Class R Certificates, and the Mortgage Loans are more particularly described in the Prospectus, dated January 27, 2004 and the Prospectus Supplement, dated May 10, 2005, as previously filed with the Securities and Exchange Commission pursuant to Rule 424(b). The Class CE Certificates, the Class P Certificates and the Class R Certificates have not been and will not be publicly offered by the Depositor. Capitalized terms used but not otherwise defined herein shall have the meanings assigned to them in the Prospectus Supplement.

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Section 9- Financial Statements and Exhibits

Item 9.01	Financial Statements and Exhibits
	(a)	Not applicable
	(b)	Not applicable
	(c)	Exhibits

Exhibit No.	Description
4.1	Pooling and Servicing Agreement, dated as of May 1, 2005, by and among Mortgage Asset Securitization Transactions, Inc. as depositor (the “Depositor”), Option One Mortgage Corporation as master servicer (the “Master Servicer”) and Wells Fargo Bank, N.A. as trustee (the “Trustee”), relating to the Series 2005-OPT1 Certificates.

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SIGNATURES

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 thereunto duly authorized.

Dated: May 27, 2005

MORTGAGE ASSET SECURITIZATION TRANSACTIONS, INC. By: /s/ Glenn McIntyre Name: Glenn McIntyre Title: Director By: /s/ Vadim Khoper Name: Vadim Khoper Title: Associate Director

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Index to Exhibits

Exhibit No.	Description	Sequentially Numbered Page
4.1	Pooling and Servicing Agreement, dated as of May 1, 2005, by and among Mortgage Asset Securitization Transactions, Inc. as depositor (the “Depositor”), Option One Mortgage Corporation as master servicer (the “Master Servicer”) and Wells Fargo Bank, N.A. as trustee (the “Trustee”), relating to the Series 2005-OPT1 Certificates.	7

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Exhibit 4.1

Filing Compare · MASTR Asset Backed Securities Trust 2005-OPT1