Peter S. Guarino, 65, a retired Social Security Administration personnel official who was active in volunteer organizations, died April 4 at Suburban Hospital after a heart attack. He lived in Rockville.

Since retiring from the government in 1977, he had chaired the legislative task force of the Gray Panthers of Montgomery County. He also had served on advisory committees, dealing with the elderly and social welfare issues, for county Democratic Dels. Jennie M. Forehand and Idamae Garrott.

He helped lobby for passage of the February 1985 Maryland law exempting Social Security benefits from Maryland taxation. He was present when Maryland Gov. Harry Hughes signed the bill into law.

Mr. Guarino, who had lived in the Washington area since 1959, was a native of Brooklyn, N.Y. He served with the Army in the European and Mediterranean theaters during World War II and earned a bachelor's degree in political science at the University of Toledo in Ohio in 1949.

He began his government career with the Labor Department in 1950 and transferred to the Social Security Administration in 1968. When he retired in 1977, he was a personnel management adviser in the office of the administrator in Baltimore.

Survivors include his wife, Louise, of Rockville; a son, Christopher, of Atlanta, and a sister, Vivian Foran of East Rockaway, N.Y.