George B. Kistiakowsky, 82, who helped develop the first atomic bomb and later became a leading opponent of nuclear weapons, died Dec. 7 at his home here. He had cancer.

In 1944, Dr. Kistiakowsky headed the explosives division of the Los Alamos Laboratory of the Manhattan Project and there he designed the arrangement of conventional explosives necessary to detonate the atomic bomb.

For his work, he received the President's Medal of Merit. After witnessing the first nuclear bomb explosion at Alamagordo, N.M., on July 16, 1945, Dr. Kistiakowsky was quoted as saying:

"I am sure that at the end of the world -- in the last millisecond of the earth's existence -- the last human will see what we saw."

He served as science adviser to President Eisenhower from July 1959 to the end of the president's term in 1961. He also served on the advisory board of the U.S. Arms Control and Disarmament Agency from 1962 to 1969, but quit as a foreign policy adviser in 1967 over the Vietnam War.

Dr. Kistiakowsky was chairman of the Council for a Livable World, a Washington and Boston-based group seeking to reduce the danger of nuclear war.

He was born in Kiev in what is now the Soviet Union. He served in the White Russian Army after the Communist October Revolution. He received a doctorate from the University of Berlin in 1925 and came to this country a year later. In 1930, he joined the faculty of Harvard University where he had been a professor of chemistry since 1938.

Survivors include his wife, Elaine, and a daughter by a previous marriage.