Wm. Irwin Buck, 73, chairman of the board and founder of the Buck Distributing Co. Inc., distributors of products of the Miller Brewing Co. and Molson's of Canada, died July 10 at his home in Upper Marlboro after a heart attack.

Mr. Buck founded the company in 1946 and remained active in it until his death.

A lifelong resident of Upper Marlboro, he attended the old Marlboro High School. Before he founded his own company he worked for his father in farming, lumbering and road-building businesses. Later he worked for the Maryland State Roads Commission and drove a beer truck.

He was chairman of the board of the United Cerebral Palsy Association of Prince George's County and a member of the Prince George's County Chamber of Commerce, the Terrapin Club and the Diamondback Club of the University of Maryland, the Prince George's Community College Foundation Board, the Prince George's Board of Trade and Citizens Concerned for a Cleaner County.

He was one of Washingtonian magazine's Washingtonians of the Year in 1981 and had also won "man of the year" awards from the National Conference of Christians and Jews and the Prince George's Board of Trade.

Survivors include his wife of 49 years, the former Katherine Rebecca Beane of Upper Marlboro; one daughter, Elizabeth Fitzgerald of Upper Marlboro; one son, Howard, of Waldorf; three sisters, Hilda Suit of Lothian and Edith Anderson and Mildred Mandell, both of Upper Marlboro; three brothers, Reginald, Russell and Eddie, all of Upper Marlboro, and three grandchildren.