Robert L. Bostick, 85, a vigorous advocate for children with mental retardation, died Oct. 24 at Providence Hospital. He had Alzheimer's disease.

Mr. Bostick, a Washington resident, worked as a graphic information specialist at the Library of Congress from the 1950s until he retired in 1978.

But it was his unpaid work for the Association for Retarded Children (now known as the Arc) that really made a mark. He was president of the organization for at least six years and repeatedly testified before Congress to get special education programs offered in the public school system.

"He was the prototype for a parent advocate, in my view," said Vincent Gray, who was executive director of the association while Mr. Bostick was president and who knew him for about 30 years. "He refused to succumb to what was then the acceptable alternative for these children. He was a real beacon, a real pioneer and a really fine man."

Mr. Bostick got involved in the issue because he had a daughter with Down syndrome. But after she got an education and a job, "his furor to do this never diminished one bit. His sense of commitment to children never diminished," Gray said.

"It was his passion," said Faye Carter Scott, who knew Mr. Bostick through a parent organization. "He was a tremendous, dedicated person, a true activist and an advocate for the retarded."

Bob Downs, who followed Mr. Bostick as president of the association, said the soft-spoken man carried a big stick and could get the District government to respond to children's needs. "He really worked very hard to get recreational facilities for people with retardation and headed the District's efforts to build a recreational center for children with retardation," Downs said.

Mr. Bostick was born in Atlanta and moved to Washington in 1941. He attended Howard and American universities. He was a member of Plymouth Congregational Church in Washington.

Survivors include his wife, Ruth Bostick, and his daughter, Barbara Bostick, both of Washington.