Frank N. von Hippel, a nuclear physicist by training, is a professor of public and international affairs at Princeton University, where he and his colleagues in the Program on Science and Global Security analyze the technical bases for nuclear-arms control and nonproliferation initiatives. He is cochair of the International Panel on Fissile Materials, whose publications may be found at www.fissilematerials.org. He is also the author of, among other books, Citizen Scientist (American Institute of Physics, 1991). During 1993 and 1994, he was Assistant Director for National Security in the White House Office of Science and Technology Policy.