KLEIN--Martin J. The editors of the Einstein Papers Project at Caltech deeply regret the death of M. J. Klein, former senior editor of The Collected Papers of Albert Einstein, Professor Emeritus of History of Physics and Physics at Yale. The recipient of many honors, Klein was a member of the Academie Internationale d'Histoire des Sciences, the National Academy of Sciences, APS, and AAAS. Author of path-breaking investigations into the birth of modern physics, Klein was among the most influential and respected historians of science. His profound understanding and discerning judgment on intellectual matters, and his warm sense of humor, will be greatly missed by all. We transmit our deepest condolences to his entire family.