8-K 1 mab03op1.txt JUNE 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): June 25, 2003 MASTR ASSET BACKED SECURITIES TRUST Mortgage Pass-Through Certificates, Series 2003-OP1 Trust (Exact name of registrant as specified in its charter) New York (governing law of 333-75724-15 54-2102389 Pooling and Servicing Agreement) (Commission 54-2102390 (State or other File Number) IRS EIN jurisdiction of Incorporation) c/o Wells Fargo Bank Minnesota, 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) ITEM 5. Other Events On June 25, 2003 a distribution was made to holders of MASTR ASSET BACKED SECURITIES TRUST, Mortgage Pass-Through Certificates, Series 2003-OP1 Trust. ITEM 7. Financial Statements and Exhibits (c) Exhibits furnished in accordance with Item 601(a) of Regulation S-K Exhibit Number Description EX-99.1 Monthly report distributed to holders of Mortgage Pass-Through Certificates, Series 2003-OP1 Trust, relating to the June 25, 2003 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 2003-OP1 Trust By: Wells Fargo Bank Minnesota, N.A., as Trustee By: /s/ Beth Belfield, Assistant Vice President By: Beth Belfield, Assistant Vice President Date: 7/1/03 INDEX TO EXHIBITS Exhibit Number Description EX-99.1 Monthly report distributed to holders of Mortgage Pass-Through Certificates, Series 2003-OP1 Trust, relating to the June 25, 2003 distribution.

MASTR Asset Backed Securitizations Mortgage Pass-Through Certificates Record Date: 45/3031/03 Distribution Date: 56/2725/03 MABS Series: 2003-OP1 Contact: Customer Service - CTSLink Wells Fargo Bank Minnesota, N.A. Securities Administration Services 7485 New Horizon Way Frederick, MD 21703 Telephone: (301) 815-6600 Fax: (301) 815-6660 Certificateholder Distribution Summary Certificate Certificate Beginning Class Pass-Through Certificate Interest Principal Class CUSIP Description Rate Balance Distribution Distribution A-1 57643LAQ9 SEN 2.32000% ~~915~~901,~~460~~440,~~217~~901.4852 1,~~887~~684,~~882~~692.4088 1418,~~019~~405,~~315~~331.9622 A-2 57643LAJ5 SEN 1.74000% ~~340~~336,~~961~~032,~~525~~357.4911 ~~527~~471,~~353~~005.8335 47,~~929~~223,~~168~~059.3828 M-1 57643LAK2 MEZ 2.17000% 58,600,000.00 ~~113~~102,~~032~~436.8906 0.00 M-2 57643LAL0 MEZ 3.17000% 51,275,000.00 ~~144~~130,~~481~~936.5541 0.00 M-3 57643LAM8 MEZ 4.07000% 21,975,000.00 7972,~~500~~047.6648 0.00 M-4 57643LAN6 MEZ 5.22000% 18,313,000.00 8477,~~972~~006.3216 0.00 MV-5 57643LAP1 MEZ 4.82000% 4,650,000.00 1918,~~922~~054.6792 0.00 MF-5 57643LAR7 MEZ 6.00000% 10,000,000.00 50,000.00 0.00 CE MAB03OP1C OC 0.00000% 10,980,010.85 5,~~215~~405,~~872~~276.2346 0.00 R-I MAB03OPR1 RES 0.00000% 0.00 0.00 0.00 R-II MAB03OPR2 RES 0.00000% 0.00 0.00 0.00 P MAB03OPTP ~~Pre_Pa~~Pre_Pay 0.00000% 100.00 ~~410~~664,~~576~~383.2664 0.00 Totals 1,~~432~~413,~~214~~266,~~853~~369.8248 8,~~533~~675,~~594~~839.8136 1825,~~948~~628,~~484~~390.3450

Certificateholder Distribution Summary (continued) Current Ending Cumulative Realized Certificate Total Realized Class Loss Balance Distribution Losses A-1 0.00 ~~901~~883,~~440~~035,~~901~~570.5230 1520,~~907~~090,~~198~~024.3610 0.00 A-2 0.00 ~~336~~328,~~032~~809,~~357~~297.1183 57,~~456~~694,~~522~~064.2163 0.00 M-1 0.00 58,600,000.00 ~~113~~102,~~032~~436.8906 0.00 M-2 0.00 51,275,000.00 ~~144~~130,~~481~~936.5541 0.00 M-3 0.00 21,975,000.00 7972,~~500~~047.6648 0.00 M-4 0.00 18,313,000.00 8477,~~972~~006.3216 0.00 MV-5 0.00 4,650,000.00 1918,~~922~~054.6792 0.00 MF-5 0.00 10,000,000.00 50,000.00 0.00 CE 0.00 10,980,010.85 5,~~215~~405,~~872~~276.2346 0.00 R-I 0.00 0.00 0.00 0.00 R-II 0.00 0.00 0.00 0.00 P 0.00 100.00 ~~410~~664,~~576~~383.2664 0.00 Totals 0.00 1,~~413~~387,~~266~~637,~~369~~978.4898 2734,~~482~~304,~~079~~229.1586 0.00 All distributions required by the Pooling and Servicing Agreement have been calculated by the Certificate Administrator on behalf of the Trustee.

Principal Distribution Statement Original Beginning Scheduled Unscheduled Face Certificate Principal Principal Realized Class Amount Balance Distribution Distribution Accretion Loss (1) A-1 939,100,000.00 ~~915~~901,~~460~~440,~~217~~901.4852 0.00 1418,~~019~~405,~~315~~331.9622 0.00 0.00 A-2 349,107,000.00 ~~340~~336,~~961~~032,~~525~~357.4911 0.00 47,~~929~~223,~~168~~059.3828 0.00 0.00 M-1 58,600,000.00 58,600,000.00 0.00 0.00 0.00 0.00 M-2 51,275,000.00 51,275,000.00 0.00 0.00 0.00 0.00 M-3 21,975,000.00 21,975,000.00 0.00 0.00 0.00 0.00 M-4 18,313,000.00 18,313,000.00 0.00 0.00 0.00 0.00 MV-5 4,650,000.00 4,650,000.00 0.00 0.00 0.00 0.00 MF-5 10,000,000.00 10,000,000.00 0.00 0.00 0.00 0.00 CE 10,981,347.20 10,980,010.85 0.00 0.00 0.00 0.00 R-I 0.00 0.00 0.00 0.00 0.00 0.00 R-II 0.00 0.00 0.00 0.00 0.00 0.00 P 100.00 100.00 0.00 0.00 0.00 0.00 Totals 1,464,001,447.20 1,~~432~~413,~~214~~266,~~853~~369.8248 0.00 1825,~~948~~628,~~484~~390.3450 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.

Principal Distribution Statement (continued) Total Ending Ending Total Principal Certificate Certificate Principal Class Reduction Balance Percentage Distribution A-1 1418,~~019~~405,~~315~~331.9622 ~~901~~883,~~440~~035,~~901~~570.5230 0.~~95989873~~94029983 1418,~~019~~405,~~315~~331.9622 A-2 47,~~929~~223,~~168~~059.3828 ~~336~~328,~~032~~809,~~357~~297.1183 0.~~96254832~~94185822 47,~~929~~223,~~168~~059.3828 M-1 0.00 58,600,000.00 1.00000000 0.00 M-2 0.00 51,275,000.00 1.00000000 0.00 M-3 0.00 21,975,000.00 1.00000000 0.00 M-4 0.00 18,313,000.00 1.00000000 0.00 MV-5 0.00 4,650,000.00 1.00000000 0.00 MF-5 0.00 10,000,000.00 1.00000000 0.00 CE 0.00 10,980,010.85 0.99987831 0.00 R-I 0.00 0.00 0.00000000 0.00 R-II 0.00 0.00 0.00000000 0.00 P 0.00 100.00 1.00000000 0.00 Totals 1825,~~948~~628,~~484~~390.3450 1,~~413~~387,~~266~~637,~~369~~978.4898 0.~~96534493~~94783921 1825,~~948~~628,~~484~~390.3450

Principal Distribution Factors Statement Original Beginning Scheduled Unscheduled Face Certificate Principal Principal Class (2) Amount Balance Distribution Distribution Accretion A-1 939,100,000.00 ~~974~~959.~~82719357~~89873445 0.00000000 1419.~~92845912~~59890450 0.00000000 A-2 349,107,000.00 ~~976~~962.~~66768495~~54832218 0.00000000 1420.~~11936277~~69010154 0.00000000 M-1 58,600,000.00 1000.00000000 0.00000000 0.00000000 0.00000000 M-2 51,275,000.00 1000.00000000 0.00000000 0.00000000 0.00000000 M-3 21,975,000.00 1000.00000000 0.00000000 0.00000000 0.00000000 M-4 18,313,000.00 1000.00000000 0.00000000 0.00000000 0.00000000 MV-5 4,650,000.00 1000.00000000 0.00000000 0.00000000 0.00000000 MF-5 10,000,000.00 1000.00000000 0.00000000 0.00000000 0.00000000 CE 10,981,347.20 999.87830728 0.00000000 0.00000000 0.00000000 R-I 0.00 0.00000000 0.00000000 0.00000000 0.00000000 R-II 0.00 0.00000000 0.00000000 0.00000000 0.00000000 P 100.00 1000.00000000 0.00000000 0.00000000 0.00000000 (2) All Classes are per $1000 denomination.

Principal Distribution Factors Statement (continued) Total Ending Ending Total Realized Principal Certificate Certificate Principal Class Loss (3) Reduction Balance Percentage Distribution A-1 0.00000000 1419.~~92845912~~59890450 ~~959~~940.~~89873445~~29982994 0.~~95989873~~94029983 1419.~~92845912~~59890450 A-2 0.00000000 1420.~~11936277~~69010154 ~~962~~941.~~54832218~~85822063 0.~~96254832~~94185822 1420.~~11936277~~69010154 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 MV-5 0.00000000 0.00000000 1,000.00000000 1.00000000 0.00000000 MF-5 0.00000000 0.00000000 1,000.00000000 1.00000000 0.00000000 CE 0.00000000 0.00000000 999.87830728 0.99987831 0.00000000 R-I 0.00000000 0.00000000 0.00000000 0.00000000 0.00000000 R-II 0.00000000 0.00000000 0.00000000 0.00000000 0.00000000 P 0.00000000 0.00000000 1,000.00000000 1.00000000 0.00000000 (3) Amount Does Not Include Excess Special Hazard, Bankrupcy, or Fraud Losses Unless Otherwise Disclosed. Please Refer to the Prospectus Supplement for a Full Description.

Interest Distribution Statement Beginning Payment of Original Current Certificate/ Current Unpaid Current Face Certificate Notional Accrued Interest Interest Class Amount Rate Balance Interest Shortfall Shortfall A-1 939,100,000.00 2.32000% ~~915~~901,~~460~~440,~~217~~901.4852 1,~~887~~684,~~882~~692.4088 0.00 0.00 A-2 349,107,000.00 1.74000% ~~340~~336,~~961~~032,~~525~~357.4911 ~~527~~471,~~353~~005.8335 0.00 0.00 M-1 58,600,000.00 2.17000% 58,600,000.00 ~~113~~102,~~032~~436.8906 0.00 0.00 M-2 51,275,000.00 3.17000% 51,275,000.00 ~~144~~130,~~481~~936.5641 0.00 0.00 M-3 21,975,000.00 4.07000% 21,975,000.00 7972,~~500~~047.6748 0.00 0.00 M-4 18,313,000.00 5.22000% 18,313,000.00 8477,~~972~~006.3217 0.00 0.00 MV-5 4,650,000.00 4.82000% 4,650,000.00 1918,~~922~~054.6792 0.00 0.00 MF-5 10,000,000.00 6.00000% 10,000,000.00 50,000.00 0.00 0.00 CE 10,981,347.20 0.00000% 10,980,010.85 0.00 0.00 0.00 R-I 0.00 0.00000% 0.00 0.00 0.00 0.00 R-II 0.00 0.00000% 0.00 0.00 0.00 0.00 P 100.00 0.00000% 100.00 0.00 0.00 0.00 Totals 1,464,001,447.20 2,~~907~~606,~~146~~179.3427 0.00 0.00

Interest Distribution Statement (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 1,~~887~~684,~~882~~692.4088 0.00 ~~901~~883,~~440~~035,~~901~~570.5230 A-2 0.00 0.00 ~~527~~471,~~353~~005.8335 0.00 ~~336~~328,~~032~~809,~~357~~297.1183 M-1 0.00 0.00 ~~113~~102,~~032~~436.8906 0.00 58,600,000.00 M-2 0.00 0.00 ~~144~~130,~~481~~936.5541 0.00 51,275,000.00 M-3 0.00 0.00 7972,~~500~~047.6648 0.00 21,975,000.00 M-4 0.00 0.00 8477,~~972~~006.3216 0.00 18,313,000.00 MV-5 0.00 0.00 1918,~~922~~054.6792 0.00 4,650,000.00 MF-5 0.00 0.00 50,000.00 0.00 10,000,000.00 CE 0.00 0.00 5,~~215~~405,~~872~~276.2346 0.00 10,980,010.85 R-I 0.00 0.00 0.00 0.00 0.00 R-II 0.00 0.00 0.00 0.00 0.00 P 0.00 0.00 ~~410~~664,~~576~~383.2664 0.00 100.00 Totals 0.00 0.00 8,~~533~~675,~~594~~839.8136 0.00 (4) Amount Does Not Include Excess Special Hazard, Bankrupcy, 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 (5) Amount Rate Balance Interest Shortfall Shortfall A-1 939,100,000.00 2.32000% ~~974~~959.~~82719357~~89873445 21.~~01031030~~79394407 0.00000000 0.00000000 A-2 349,107,000.00 1.74000% ~~976~~962.~~66768495~~54832218 1.~~51057936~~34917189 0.00000000 0.00000000 M-1 58,600,000.00 2.17000% 1000.00000000 1.~~92888891~~74805563 0.00000000 0.00000000 M-2 51,275,000.00 3.17000% 1000.00000000 2.~~81777786~~55361112 0.00000000 0.00000000 M-3 21,975,000.00 4.07000% 1000.00000000 3.~~61777793~~27861115 0.00000000 0.00000000 M-4 18,313,000.00 5.22000% 1000.00000000 4.~~64000000~~20500027 0.00000000 0.00000000 MV-5 4,650,000.00 4.82000% 1000.00000000 43.~~28444516~~88277849 0.00000000 0.00000000 MF-5 10,000,000.00 6.00000% 1000.00000000 5.00000000 0.00000000 0.00000000 CE 10,981,347.20 0.00000% 999.87830728 0.00000000 0.00000000 0.00000000 R-I 0.00 0.00000% 0.00000000 0.00000000 0.00000000 0.00000000 R-II 0.00 0.00000% 0.00000000 0.00000000 0.00000000 0.00000000 P 100.00 0.00000% 1000.00000000 0.00000000 0.00000000 0.00000000 (5) All Classes are per $1000 denomination.

Interest Distribution Factors 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 21.~~01031030~~79394407 0.00000000 ~~959~~940.~~89873445~~29982994 A-2 0.00000000 0.00000000 1.~~51057936~~34917189 0.00000000 ~~962~~941.~~54832218~~85822063 M-1 0.00000000 0.00000000 1.~~92888891~~74805563 0.00000000 1000.00000000 M-2 0.00000000 0.00000000 2.~~81777767~~55361112 0.00000000 1000.00000000 M-3 0.00000000 0.00000000 3.~~61777747~~27861115 0.00000000 1000.00000000 M-4 0.00000000 0.00000000 4.~~64000000~~20499973 0.00000000 1000.00000000 MV-5 0.00000000 0.00000000 43.~~28444516~~88277849 0.00000000 1000.00000000 MF-5 0.00000000 0.00000000 5.00000000 0.00000000 1000.00000000 CE 0.00000000 0.00000000 ~~474~~492.~~97562321~~22343685 0.00000000 999.87830728 R-I 0.00000000 0.00000000 0.00000000 0.00000000 0.00000000 R-II 0.00000000 0.00000000 0.00000000 0.00000000 0.00000000 P 0.00000000 0.00000000 ~~4105762~~6643836.~~60000000~~40000000 0.00000000 1000.00000000 (6) Amount Does Not Include Excess Special Hazard, Bankrupcy, or Fraud Losses Unless Otherwise Disclosed. Please Refer to the Prospectus Supplement for a Full Description.

CERTIFICATEHOLDER ACCOUNT STATEMENT CERTIFICATE ACCOUNT Beginning Balance 0.00 Deposits Payments of Interest and Principal 2835,~~604~~153,~~007~~498.8536 Liquidations, Insurance Proceeds, Reserve Funds 10.2400 Proceeds from Repurchased Loans 0.00 Other Amounts (Servicer Advances) 0.00 Realized ~~Losses~~Loss (Gains, Subsequent Expenses & Recoveries) 0.00 Prepayment Penalties ~~410~~664,~~576~~383.2664 Total Deposits 2935,~~014~~817,~~585~~882.3500 Withdrawals Reimbursement for Servicer Advances 0.00 Payment of Service Fee 1,~~532~~513,~~506~~652.2014 Payment of Interest and Principal 2734,~~482~~304,~~079~~229.1586 Total Withdrawals (Pool Distribution Amount) 2935,~~014~~817,~~585~~882.3500 Ending Balance 0.00

SERVICING FEES Gross Servicing Fee ~~596~~588,~~756~~860.2996 Radian ~~932~~921,~~167~~258.4300 Trustee Fee - Wells Fargo 3,~~582~~533.4818 Supported Prepayment/Curtailment Interest Shortfall 0.00 Net Servicing Fee 1,~~532~~513,~~506~~652.2014

OTHER ACCOUNTS Beginning Current Current Ending Account Type Balance Withdrawals Deposits Balance Reserve Fund 1,000.0100 0.00 0.0001 1,000.0001 Reserve Fund 0.00 0.00 0.00 0.00

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 916 01 0 917 ~~949~~1,~~365~~620,829.5573 0115,865.0076 0.00 ~~949~~1,~~365~~736,695.5549 30 Days ~~113~~105 21 23 0 ~~117~~109 1614,~~133~~453,~~658~~547.3367 ~~165~~50,~~208~~310.1065 ~~255~~362,~~688~~952.0999 0.00 1614,~~554~~866,~~554~~811.5231 60 Days 1822 03 3547 0 5372 3,~~551~~001,~~476~~477.3579 0306,502.0074 46,~~315~~769,~~829~~516.2089 0.00 710,~~867~~077,~~305~~497.5542 90 Days 2 3 418 71 0 4682 ~~235~~482,~~734~~479.63 ~~411~~985,~~893~~884.7723 611,~~771~~426,~~661~~088.5710 0.00 712,~~419~~894,~~289~~451.9796 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 ~~133~~130 1428 78122 0 ~~225~~280 1917,~~920~~937,~~869~~505.3109 12,~~526~~963,~~467~~527.4235 1118,~~343~~674,~~178~~423.8674 0.00 3239,~~790~~575,~~515~~456.5918 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.~~094073~~169924% 0.~~000000~~010620% 0.000000% 0.~~094073~~180544% 0.~~067160~~116768% 0.~~000000~~008347% 0.000000% 0.~~067160~~125115% 30 Days 1.~~181144~~115123% 0.~~020905~~010620% 0.~~020905~~031861% 0.000000% 1.~~222954~~157604% 1.~~141326~~041260% 0.~~011687~~003624% 0.~~018088~~026148% 0.000000% 1.~~171101~~071033% 60 Days 0.~~188147~~233645% 0.~~000000~~031861% 0.~~365841~~499150% 0.000000% 0.~~553988~~764656% 0.~~251238~~216232% 0.~~000000~~022081% 0.~~305310~~487689% 0.000000% 0.~~556549~~726002% 90 Days 0.~~020905~~031861% 0.~~031358~~084962% 0.~~428556~~754036% 0.000000% 0.~~480819~~870858% 0.~~016676~~034759% 0.~~029138~~071025% 0.~~479041~~823157% 0.000000% 0.~~524855~~928940% 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 1.~~390195~~380629% 0.~~146336~~297366% 01.~~815303~~295667% 0.000000% 2.~~351834~~973662% 1.~~409241~~292251% 0.~~107985~~213498% 01.~~802439~~345340% 0.000000% 2.~~319665~~851089%

OTHER INFORMATION Current Period Class A Insufficient Funds 0.00 Principal Balance of Contaminated Properties 0.00 Periodic Advance ~~481~~626,~~552~~714.8438 Class A-1 524,901,347.20 35.85388172% ~~511~~504,~~825~~602,~~367~~308.9668 36.~~21577496~~36411775% 63.~~784218~~635875% 0.000000% Class A-2 175,794,347.20 12.00779873% 175,793,010.85 12.~~43877408~~66850674% 23.~~777001~~695611% 0.000000% Class M-1 117,194,347.20 8.00507045% 117,193,010.85 8.~~29235121~~44550327% 4.~~146423~~223003% 0.000000% Class M-2 65,919,347.20 4.50268320% 65,918,010.85 4.~~66423119~~75037523% 3.~~628120~~695128% 0.000000% Class M-3 43,944,347.20 3.00166009% 43,943,010.85 3.~~10932262~~16674893% 1.~~554909~~583626% 0.000000% Class M-4 25,631,347.20 1.75077335% 25,630,010.85 1.~~81353009~~84702431% 1.~~295793~~319725% 0.000000% Class CE 0.00 0.00000000% 0.00 0.00000000% 0.~~776924~~791273% 0.000000% Class R-I 0.00 0.00000000% 0.00 0.00000000% 0.000000% 0.000000% Class R-II 0.00 0.00000000% 0.00 0.00000000% 0.000000% 0.000000% Please Refer to the Prospectus Supplement for a Full Description of Loss Exposure

COLLATERAL STATEMENT Collateral Description Mixed Fixed & Arm Weighted Average Gross Coupon 8.~~090213~~087739% Weighted Average Net Coupon 7.~~590213~~587739% Weighted Average Pass-Through Rate 6.~~806183~~802502% Weighted Average Maturity(Stepdown Calculation ) ~~351~~350 Beginning Scheduled Collateral Loan Count 9,~~669~~567 Number Of Loans Paid In Full ~~102~~151 Ending Scheduled Collateral Loan Count 9,~~567~~416 Beginning Scheduled Collateral Balance 1,~~432~~413,~~214~~266,~~853~~369.8349 Ending Scheduled Collateral Balance 1,~~413~~387,~~266~~637,~~369~~978.4999 Ending Actual Collateral Balance at 3031-~~Apr~~May-2003 1,~~413~~388,~~588~~081,~~372~~939.9520 Monthly P &I Constant 10,~~740~~601,~~861~~405.1223 Special Servicing Fee 0.00 Prepayment Penalties ~~410~~664,~~576~~383.2664 Realized Loss Amount 0.00 Cumulative Realized Loss 0.00 Ending Scheduled Balance for Premium Loans 1,~~413~~387,~~266~~637,~~369~~978.4999 Scheduled Principal 1,~~085~~076,~~091~~297.7332 Unscheduled Principal 1724,~~863~~552,~~392~~093.6118

~~Other~~Miscellaneous ~~Income~~Reporting ~~(247~~Net Monthly Excess Cashflow 5,405,276.~~96)~~46 Extra Prinicpal Distribution Amount 0.00 OC Amount 10,980,010.85 OC Deficiency Amount 0.00 OC Release Amount 0.00 OC Target Amount 10,980,010.85 Stepdown NO Trigger Event NO Credit Enhancement Percentage 12.668507%

~~Miscellaneous~~Group ~~Reporting~~Level Collateral Statement Group Group 1 Group 2 Group 3 Collateral Description Fixed 15/30 & ARM Fixed 15/30 & ARM Fixed 15/30 & ARM Weighted Average Coupon Rate 7.684790 8.271919 7.632167 Weighted Average Net ~~Monthly~~Rate ~~Excess~~7.184790 ~~Cashflow~~7.771919 57.132167 Pass-Through Rate 6.273448 7.028069 6.225589 Weighted Average Maturity 350 350 341 Beginning Loan Count 820 6,~~215~~646 1,~~872~~454 Loans Paid In Full 20 101 15 Ending Loan Count 800 6,545 1,439 Beginning Scheduled Balance 103,839,321.2182 ~~Extra~~926,511,187.64 ~~Prinicpal~~204,296,625.81 ~~Distribution~~Ending ~~Amount~~scheduled Balance 101,463,543.61 910,481,634.63 202,039,979.50 Record Date 05/31/2003 05/31/2003 05/31/2003 Principal And Interest Constant 772,696.32 7,014,875.04 1,510,040.47 Scheduled Principal 107,710.18 628,187.26 210,685.43 Unscheduled Principal 2,268,068.03 15,401,365.75 2,045,960.88 Scheduled Interest 664,986.14 6,386,687.78 1,299,355.04 Servicing Fees 43,266.41 386,046.30 85,123.59 Master Servicing Fees 0.00 OC0.00 0.00 Trustee Fee 259.61 2,316.27 510.75 FRY Amount 100.00 0.00 0.00 Special Hazard Fee 0.00 0.00 0.00 Other Fee 78,~~980~~601.36 572,~~010~~004.8536 OC153,831.71 ~~Deficiency~~Pool ~~Amount~~Insurance Fee 0.00 OC0.00 ~~Release~~0.00 ~~Amount~~Spread Fee 1 0.00 OC0.00 ~~Target~~0.00 ~~Amount~~Spread 10Fee 2 0.00 0.00 0.00 Spread Fee 3 0.00 0.00 0.00 Net Interest 542,~~980~~858.76 5,~~010~~426,320.85 ~~Stepdown~~1,059,888.99 NORealized ~~Trigger~~Loss ~~Event~~Amount NO0.00 ~~Credit~~0.00 ~~Enhancement~~0.00 Cumulative Realized Loss 0.00 0.00 0.00 Percentage 12of Cumulative Losses 0.~~438774%~~00 0.00 0.00 Prepayment Penalties 0.00 0.00 0.00 Special Servicing Fee 0.00 0.00 0.00

Group Level Collateral Statement Group Group 14 ~~Group~~Total ~~2 Group 3~~ Collateral Description Fixed 15/30 & ARM ~~Fixed~~Mixed ~~15/30 & ARM~~ Fixed ~~15/30~~ & ~~ARM~~Arm Weighted Average Coupon Rate 7.~~693757~~887699 8.~~276021~~087739 ~~7.631666~~ Weighted Average Net Rate 7.~~193758~~387699 7.~~776021~~587739 7Pass-Through Rate 6.~~131665~~599875 6.802502 Weighted Average Maturity ~~351~~341 ~~351~~350 ~~342~~ Beginning Loan Count ~~828~~647 69,~~720~~567 ~~1,465~~ Loans Paid In Full 815 74151 11 Ending Loan Count ~~820~~632 69,~~646~~416 ~~1,454~~ Beginning Scheduled Balance ~~105~~178,~~113~~619,~~054~~234.0822 ~~939~~1,~~256~~413,~~771.34 206~~266,~~070,259~~369.7949 Ending scheduled Balance ~~103~~173,~~839~~652,~~321~~821.8225 ~~926~~1,~~511~~387,~~187.64 204~~637,~~296,625~~978.8199 Record Date 0405/3031/2003 0405/3031/2003 ~~04/30/2003~~ Principal And Interest Constant ~~782~~1,~~657.30 7~~303,~~110,814~~793.5540 110,~~521~~601,~~498~~405.4923 Scheduled Principal ~~108~~129,~~728~~714.7445 ~~633~~1,~~057.44 210~~076,~~949~~297.0732 Unscheduled Principal 14,~~165~~836,~~003~~698.52 1224,~~112~~552,~~526~~093.2618 ~~1,562,684.91~~ Scheduled Interest ~~673~~1,~~928.56 6~~174,~~477,757~~078.1195 19,~~310~~525,~~549~~107.4291 Servicing Fees 4374,~~796~~424.9866 ~~391~~588,~~357~~860.1196 ~~85,862.73~~ Master Servicing Fees 0.00 0.00 ~~0.00~~ Trustee Fee ~~262~~446.9655 23,~~349~~533.4118 ~~515.47~~ FRY Amount 0.00 0.00 ~~0.00~~ Special Hazard Fee 0.00 0.00 ~~0.00~~ Other Fee 79116,~~646~~820.4857 ~~578~~921,~~055~~258.6900 ~~155,159.52~~ 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 ~~550~~982,~~222~~387.1417 58,~~505~~011,~~994~~455.9077 ~~1,069,011.70~~ Realized Loss Amount 0.00 0.00 ~~0.00~~ Cumulative Realized Loss 0.00 0.00 ~~0.00~~ Percentage of Cumulative Losses 0.00 0.00 ~~0.00~~ Prepayment Penalties 0.00 0.00 ~~0.00~~ Special Servicing Fee 0.00 0.00 ~~0.00 Pass-Through Rate 6.281490 7.034492 6.225129~~

Group Level Collateral Statement Group Group 4 Total Collateral Description Fixed 15/30 & ARM Mixed Fixed & Arm Weighted Average Coupon Rate 7.879208 8.090213 Weighted Average Net Rate 7.379208 7.590213 Weighted Average Maturity 342 351 Beginning Loan Count 656 9,669 Loans Paid In Full 9 102 Ending Loan Count 647 9,567 Beginning Scheduled Balance 181,774,768.62 1,432,214,853.83 Ending scheduled Balance 178,619,234.22 1,413,266,369.49 Record Date 04/30/2003 04/30/2003 Principal And Interest Constant 1,325,890.78 10,740,861.12 Scheduled Principal 132,356.48 1,085,091.73 Unscheduled Principal 3,023,177.92 17,863,392.61 Scheduled Interest 1,193,534.30 9,655,769.39 Servicing Fees 75,739.47 596,756.29 Master Servicing Fees 0.00 0.00 Trustee Fee 454.64 3,582.48 FRY Amount 0.00 0.00 Special Hazard Fee 0.00 0.00 Other Fee 119,305.74 932,167.43 Pool Insurance Fee 0.00 0.00 Spread Fee 1 0.00 0.00 Spread Fee 2 0.00 0.00 Spread Fee 3 0.00 0.00 Net Interest 998,034.45 8,123,263.19 Realized Loss Amount 0.00 0.00 Cumulative Realized Loss 0.00 0.00 Percentage of Cumulative Losses 0.00 0.00 Prepayment Penalties 0.00 0.00 Special Servicing Fee 0.00 0.00 Pass-Through Rate 6.588601 6.806183

Filing Compare · MORTGAGE ASSET SECURITIZATION TRANSACTIONS INC SER 2003-OPT1