Isador William Mendelsohn, 88, a retired government civil engineer an dmojor in the Arimy Reserves, died of cancer Sept. 14 at the Bethesda Naval Hospital. He had homes in Gaithersburg and Hollywood, Fla.

Maj. Mendelsohn, who was born in New York, graduated from the old Western High School here and from the University of Wisconsin, where he also earned a master's degree in civil engineering.

After Army service in World War I, he was a sanitary engineer with the Public Health Service and the Public Works Administration. He was recalled to active duty in the Army in 1940 and served with the Corps of Engineers in Europe during World War II. He retired from the Reserves about 1953.

After the war, he remained with the corps as a civilian until 1951. He later worked for the Interior Department and then for AID, which assigned him to Korea. He retied in 1962.

Maj. Mendelsohn was a founder of Congregation Beth El in Bethesda and the American Society for Technion and a member of the Gaithersburg Hebrew Congregation and the Zionist Organization of America. He was a fellow of the American Public Health Association and a member of other professional groups.

Survivors include his wife, Mildred K., of Gaithersburg and Hollywood+ two sons, Morton D., of St. Louis, and Eric S., of Rockville; two daughters, Carol M. Barrons of Gaithersburg, and Charla M. Wallace of Sistersville, W. Va.; three sisters, Minnie Millstein of Silver Spring, Eva Rosenberg of Washington, and Frances Rubinstein of Chevy Chase; a brother, Dr. Matthew Mendelsohn of Carmel, Calif., and 13 grandchildren.