AbstractIn April 1974, the US Arms Control and Disarmament Agency asked the National Academy of Sciences to arrange for a study of long-term, world-wide environmental risks to be expected from multiple detonations — no matter what the cause — of nuclear weapons.The study has been completed and its results published in ‘Long-Term, Worldwide Effects of Multiple Nuclear Weapons Detonations.’The results led NAS President Philip Handler to give warning in a letter transmitting the report to Dr Fred C Ikle, Director of the Arms Control and Disarmament Agency. The following is the text of the letter: