Mary Crosby Smith, 47, a former teacher at the Georgetown University School of Nursing who was active in church and volunteer groups, died of cancer Oct. 7 at her home in McLean.

Mrs. Smith was born in Boston, Mass. She earned nursing degrees at the Catherine Laboure School of Nursing and at Boston College. She taught at the nursing school of Massachusetts General Hospital.

About 1961, she moved to Washington and took a master's in nursing at Catholic University. She taught at the Georgetown nursing school for about a year before her marriage in 1965 to Dr. Bernard F. Smith, a physician.

Mrs. Smith was a member of St. John's Catholic Church in McLean and the board of the St. John's Parent-Teachers Organization. She arranged prayer services for persons who were ill. She also was a volunteer with Hope of Northern Virginia, a pregnancy counseling service, and with SOME (So Others May Eat), a Washington-based group that assists the needy.

In addition to her husband, of McLean, survivors include three children, Maria, Meg and Eileen, all of McLean; her mother, Katherine Crosby, of Arlington, Mass.; three sisters, Catherine Thompson, of Alexandria, Terese Maloy, of Rochester, N.Y., and Anne Towle, of Arlington, Mass.; and a brother, John J. Crosby Jr., of Arlington, Mass.