Maria Prati, 78, who with her husband founded and operated the old Aldo Cafe on New Hampshire Avenue in northeast Washington for many years, died of cardiac arrest Saturday at Georgetown University Hospital. She had been suffering from a heart ailment and diabetes.

Mrs. Prati was born in Petorano Sul Gizio, Italy. She came to the United States in 1919 and lived first in Yorksville, Ohio, where she met and married her husband, Aldo Prati, who was born in Verona, Italy.

The couple moved to Washington in 1925 when Mr. Prati became a waiter at the Mayflower Hotel. At the same time, Mrs. Prati began serving meals at their home at 1143 New Hampshire Ave. NW. The family also took in boarders.

About 1930, the Pratis opened the Aldo Cafe in the basement of their building. Mrs. Prati did the cooking. After World War II, the Pratis two sons, Henry and Ermanno, took over the major responsibility for running the restaurant and shortened the name to Aldo's. Their father died in 1953. The business continued in the same location until 1965, when the property was sold.

The sons later opened several other restaurants, including Aldo's Channel House in Foggy Bottom and Aldo's Rotunda on Capitol Hill. Mrs. Prati continued to live in the same section of New Hampshire Avenue where the original Aldo's was located.

In addition to her sons, Henry of Bethesda and Ermanno of Chevy Chase, Mrs. Prati is survived by two sisters, Margarita Castro, of Vienna, and Antonina DeAngelis, of Hamilton, Ontario, Canada; two brothers, Armando DeSantis, also of Hamilton, And Frank DeSantis, of Buffalo, N.Y., and five grandchildren.