The project of abolishing all nuclear weapons has been given fresh impetus but the old questions remain. Having regard to the manifold problems of definition and verification, is 'Global Zero' realistic in a world in which proliferation seems more likely than abolition? Is it even desirable under present and foreseeable security conditions? Familiar arguments for extended deterrence still seem to underpin security judgments about the possibility of war between the major states and the complexities of the nuclear fuel cycle continue to present a major challenge to international control.