Nuclear proliferation became an increasingly major concern after France and then China joined the nuclear “club” in the 1960s. However, it was not until India’s “peaceful nuclear explosive” test of 1974 that a real sense of potential worldwide crisis emerged, which also spawned a substantial amount of serious writing on the issue. The basic puzzle facing the study of nuclear proliferation is why there is a considerable and persistent disparity between the number of nuclear weapons-capable states and the number of actual nuclear weapons states. Three early works that represented crucial conceptual breakthroughs in the struggle toward a proper descriptive inference of the dynamics of proliferation are William Epstein’s The Last Chance (1976), Stephen M. Meyer’s The Dynamics of Nuclear Proliferation (1984), and Opaque Nuclear Proliferation (1991), edited by Benjamin Frankel. More contemporary political science work features attempts by each of the major international relations paradigms to tackle the proliferation puzzle: realism, psychological constructivism, neoliberal institutionalism, liberalism, and sociological constructivism. While scholars disagree over a host of issues, a consensus on the dynamics of nuclear proliferation may be discerned. In particular, there are five points on which most recent works converge: that proliferation has been historically rare; that we cannot take the demand for nuclear weapons for granted; that domestic politics and identity considerations play a crucial role in shaping proliferation choices; and that theory-guided, in-depth comparative case studies are the most appropriate means of advancing the state of our knowledge at this point in time.