Mardelle L. Reynolds, 79, a retired official of the Armed Forces Institute of Pathology, died Monday at the Randolph Hills Nursing Home in Wheaton. She had arteriosclerosis.

Mrs. Reynolds came to Washington in 1941 and worked for the Selective Service Systems and the Civil Service Commission before joining the institute in 1946.

She was chief of the agency's medical statistics division from 1948 until retiring in 1962.

She was a fellow of the American Public Health Association and a member of the Royal Society of Health.She also was a member of the Bethesda Baptist Church and the Daughters of the American Revolution.

Mrs. Reynolds was a graduate of North Georgia College in her native Dahlonega, Ga. She began her government career as a clerk in the Selective Service in Denver in 1940. She had lived in Chevy Chase since 1941.

Her first husband, Evert B. Clark Sr., died in 1938, and her second husband, Lester T. Reynolds, in 1969.

Mrs. Reynolds' survivors include five children by her first marriage, Evert B., of Potomac, David J., of Kennewich, Wash., James E., of Birmingham, Ala., Robert A., of Rockville, and Mary L. Barnes of Rockville; 15 grandchildren, and eight great-grandchildren.

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