Joseph Musher, 69, a longtime actuary for government and private industry who was an authority on actuarial aspects of collectively bargained pension plans, died Thursday at Suburban Hospital of complications following a stroke. He lived in Bethesda.

Mr. Musher, a New York City native who earned both bachelor's and master's degrees from the City College of New York by the age of 19, came to Washington in 1934 to work for the Veterans Administration.

In 1942, he became chief actuary of the Railroad Retirement Board and moved with it to Chicago. He remained there until 1955, when he joined the Washington actuarial firm of Murray W. Latimer. He specialized in employe benefit systems for industrial and union organizations and wrote a number of papers for professional journals.

After retiring from the Latimer firm in 1979, Mr. Musher became an actuary for the Pension Benefit Guaranty Corporation, which was established in 1974 to guarantee payment of insured benefits if covered plans terminate without assets to pay such benefits. Mr. Musher had urged the creation of such an agency for many years.

He was a member of Phi Beta Kappa and the Ohr Kodesh Synagogue in Silver Spring and a fellow of the Society of Actuaries. He was a founder the American Academy of Actuaries in 1965.

Survivors include his wife, the former Viola Wishner, of Bethesda; two daughters, Francine Ostrovsky of Lancaster, Pa., and Andrea, of Madison, Wis.; a son, Steven, of Gaithersburg, and a sister, Ida Slotnick of New York City.