The proliferation of nuclear weapons has been widely characterized as one of the major threats to international security in the contemporary period. Many analysts, scholars, and policymakers have expressed the belief that the risks of nuclear proliferation are higher today than ever before and some even describe the danger from new nuclear weapons states as greater than that posed by the Soviet Union during the Cold War. This paper challenges this common perspective. It demonstrates that the nuclear non-proliferation treaty regime has become progressively more robust, to the point where all of the non-nuclear weapons states have become members. It argues that the decline in inter-state conflict generally, and the diffusion of international norms has transformed the international security environment to such an extent that the risk of proliferation remains confined to a very small number of “rogue” states. The article examines the efforts of counter-proliferation directed against these states and points out their limitations. An assessment of the threat posed by such small nuclear arsenals leads to the conclusion that the threat or the use of military force is not an effective or advisable instrument of counterproliferation, but that instead traditional diplomatic tools of international law, sanctions, and deterrence are more appropriate to containing this threat.