Warren H. Donnelly, 77, a senior Congressional Research Service expert on nuclear nonproliferation issues who retired from the Library of Congress in 1993, died Sept. 1 at the Hospice of Northern Virginia. He had polymyocitis, an immune deficiency disease.

Dr. Donnelly joined the staff of the Library of Congress in 1965. During the course of his career, he provided information and analyses to congressional committees on U.N. efforts to monitor nuclear proliferation in Iraq, North Korea's nuclear program, dismantlement and disposal of nuclear warheads and efforts to strengthen the inspection authority of the International Atomic Energy Agency. He retired as senior specialist in energy policy in the Environment and Natural Resources Policy Division.

He received the library's Distinguished Service Award in 1992.

Dr. Donnelly continued to do consulting work for the Library of Congress after he retired.

A resident of McLean, Dr. Donnelly was born in Mount Vernon, N.Y., and graduated from Queens College.

During World War II, he served in the Army Air Forces in Europe and received a Bronze Star Medal. He received a master's degree and a doctorate in public administration at New York University after the war.

From 1946 to 1948, Dr. Donnelly was an engineer with Western Electric. He began his federal career in 1948 with the Atomic Energy Commission in New York and relocated to the Washington area in 1963.

Survivors include his wife of 51 years, Gloria L. Donnelly of McLean; a son, Brian C. Donnelly of Colleyville, Tex.; a brother; a sister; and two granddaughters.