Dr. Lewis W. Butz, 74, who was head of the chemistry branch of the Office of Naval Research for more than 20 years before retiring in 1969, died Saturday at the Woodbine nursing home in Alexandria. He had Parkinson's disease.

Dr. Butz was a native of Pennsylvania and a 1927 graduate of the University of Pennsylvania. He earned master's and doctoral degrees in chemistry at the University of Illinois before coming to Washington in the mid-1930s.

He spent 10 years as a chemical researcher with the Agriculture Department's Bureau of Animal Husbandry before joining the Office of Naval Research in 1946. He became director of its chemistry branch shortly after joining.

Dr. Butz was a member of the Cosmos Club. His professional memberships included the American Institute of Chemists and the American Chemical Society.

He was a resident of Alexandria for the past 34 years.

Survivors include his wife, Eleanore, and a son, Andrew, both of Alexandria; another son, Eric of Drain, Ore., and one grandchild.

The family suggests that expressions of sympathy be in the form of contributions to Georgetown University's Parkinson's Disease Research Fund, to the American Parkinson's Disease Foundation, or to a charity of one's choice.