Fitch Rates MASTR Alternative Loan Trust Mtge P-T Certs $851.7MM Series 2003-7.

Business Editors

NEW YORK--(BUSINESS WIRE)--Oct. 31, 2003

MASTR Alternative Loan Trust 2003-7 classes 1-A-1, 2-A-1, 3-A-1 through 3-A-5, 4-A-1, 4-A-2, 4-A-3, 5-A-1, 6-A-1, 7-A-1 through 7-A-18, 8-A-1, 15-A-X, 30-A-X, 15-PO, 30-PO, A-LR, A-MR and A-UR ($837.9 million) are rated 'AAA', by Fitch Ratings. In addition, classes B-2 ($7.7 million) and B-3 ($6.1 million) are rated 'A-' and 'BBB-' respectively by Fitch.

The 'AAA' rating on the senior certificates reflects the 5.25% subordination provided by the 2.50% class B-1 (NR - Not rated by Fitch), the 0.87% class B-2, the 0.69% class B-3, the 0.54% privately offered class B-4 (NR), the 0.30% privately offered class B-5 (NR), and the 0.35% privately offered class B-6 (NR) certificates. Classes B-2 and B-3 are rated 'A-' and 'BBB-' based on their respective subordination.

Fitch Ratings believes the above credit enhancement will be adequate to support mortgagor defaults as well as bankruptcy, fraud and special hazard losses in limited amounts. In addition, the ratings reflect the quality of the mortgage collateral, the strength of the legal and financial structures, and Wells Fargo Bank Minnesota, N.A. as Master Serivcer. Fitch currently rates Wells Fargo a 'RMS1' for Master Servicing.

The trust consists of 4,673 conventional, fully amortizing 15 to 30-year fixed-rate mortgage loans secured by first liens on one to four-family residential properties with an aggregate scheduled principal balance of $884,332,942. The average unpaid principal balance of the aggregate pool as of the cut-off date (October 1, 2003) is $189,243. The weighted average original loan-to-value ratio (LTV) is 69.60%. The weighted average credit score of the ...