Benjamin Ginzburg, 81, who was research director of the Senate constitutional rights subcommittee from 1955 to 1957, died of pneumonia Sunday at Arlington Hospital.

He came to Washington in the early days of the New Deal, and joined the Works Progress Administration as an economic editor and speech writer. He later worked as an economist in the Office of Price Administration before moving in 1947 to Norwalk, Conn., and operating a radio station.

Dr. Ginzburg returned to Washington in 1951, and worked as an economist and speech writer for the Office of Price Stabilization before joining the Senate Judiciary Committee's constitutional rights subcommittee.

He wrote a book about his years on the subcommittee, "Rededication to Freedom," which was published in 1959.

Dr. Ginzburg was born in Russia and came to this country in 1906. He earned a bachelor's degree at Columbia University and master's and doctoral degrees at Harvard University.

He studied at the University of Paris and was a reporter for the European edition of the Chicago Tribune before coming to Washington.

He is survived by his wife, Rose, of the home in Arlington; three daughters, Judith Glazer, of Norwalk, Helen Yaker, of Summit, N.J., and Diana Stein, of Alexandria; two sisters, Sarah Wolfson and Ruth Skodnick, both of New York City; nine grandchildren, and two great-grandchildren. CAPTION: Picture, BENJAMIN GINZBURG