Josephine Weeks, 79, a longtime resident of Alexandria who was active in the restoration of that city's Old Town neighborhood and the preservation of historic buildings elsewhere, died of leukemia Monday at the Circle Terrace Hospital in Alexandria.

A native of Washington, Mrs. Weeks studied at George Washington University and at the University of Paris. During the 1920s, she worked for the State Department in Washington and for the Mexican Claims Commission, a government agency. In 1930, she married Mangum Weeks, an attorney, and the couple made their home in Alexandria.

Mrs. Weeks was a founding member of the Alexandria Architectural Forum and a member of the Friends of Stratford, which sees to the care of Stratford Hall, Gen. Robert E. Lee's birthplace. She also was a member of the Alexandria Association and of other civic groups. She helped resuscitate the Alexandria Library Society, an old organization that had virtually ceased to function.

Her husband died in 1977.

Survivors include two brothers, Carl F. Schaefer of Easton, Md., and William E. Schaefer of Hagerstown, Md., and three sisters, Catherine and Mary Schaefer of Silver Spring, and Agnes Shay of Yonkers, N.Y.

The family suggests that expressions of sympathy be in the form of contributions to the American Cancer Society, or to a charity of one's choice.