John N. Nietmann Jr., 65, retired associate general counsel of the American Council of Life Insurance, died of cancer Friday at his home in Bethesda.

His retirement on Nov. 1 had ended 48 years with the insurance group. He had joined a predecessor group, Association of Life Insurance Presidents, as a mail clerk at the age of 16.

Mr. Nietmann rose to attorney, assistant counsel and assistant general counsel to become associate general counsel in 1973.

He participated in legislative and regulatory activities in various states and played a prominent role in forming consumer-related insurance codes.

He also was responsible for the development and production of all the council's state legal manuals and bulletins.

Mr. Nietmann was born in Brooklyn, N.Y. He earned a law degree from St. John's University and was admitted to the New York State Bar. He served as an Army officer during World War II and later remained active with the Army National Guard and the Army Reserve.

He is survived by his wife, Ethel, of the home; a son, Hohn S., of Clinton; two daughters, Stefani Hochrain, of Seaford, N.Y., and Monica Reed, of Coventry, Conn.; his father, John J. Jr., also of Seaford, and three grandchildren.