Mary Trail Flatcher, 48, a research chemist with the National Institutes of Health, died of cancer Friday at the Washington Home Hospice.

She had worked for NIH for the past 23 years, and was working in the drug development branch of the National Cancer Institute at the time of her death. Prior to joining NIH, she had worked for the National Bureau of Standards for about five years.

Mrs. Flather was born in Washington and reared in Bethesda. She was a graduate of Bethesda-Chevy Chase High School and earned a bachelor's degree in chemistry at American Univeristy. She also did graduate work in chemistry at American University.

She was the author of several technical works and a member of the American Chemical Society. Mrs. Flather was a resident of Kensington where she was a member of St. Paul's United Methodist Church.

Survivors include her husband, A. Chester Flather Jr., and a daughter, Margie Flather, both of Kensington; another daughter, Mary Flather Phillips of College Park; her stepfather and mother, Mr. and Mrs. William T. Baxter of Kensington, and a sister, Nancy Trail Mikolajczyk of Aiea, Hawaii.

The family suggests that expressions of sympathy be in the form of contributions to St. Paul's United Methodist Church in Kensington or the Washington Home Hospice in Washington.