The nuclear nonproliferation regime was established in the late 1950's and 1960's, especially with the creation of the Treaty on the Non-Proliferation of Nuclear Weapons (NPT) in 1968, and has altered considerably in subsequent decades. It has also been subject to the challenges posed by several external shocks. This thesis seeks to examine the relationship, if any, between shocks and the ways in which the regime has changed from its inception to the present day. While there is a wide theoretical literature on international regimes, much of it ignores the ways in which regimes change and develop over time. Instead, most regime theory focuses on the reasons behind regime creation and decay, rather than on the processes that occur in between. When the question of regime change has been examined, it has also commonly been assumed that such change occurs in a gradual, incremental fashion. This dissertation will examine the nuclear nonproliferation regime in order to challenge the assumptions in regime theory regarding the existence and manner of regime change. Specifically, the relationship between certain shocks and subsequent change (or its absence) will be examined through four contrasting case studies of shocks and their aftermaths. They involve the Indian nuclear test of 1974, the Israeli attack on Iraq's nuclear reactor in 1981, the post-Gulf War revelations of Iraq's nuclear weapon programme, and the Indian and Pakistani nuclear tests of 1998. These case studies make it possible to understand both the implications for regime theory generally, and the circumstances under which such change occurs, or fails to occur. The thesis ultimately asserts that the nonproliferation regime has indeed changed considerably since its creation, of necessity for its survival, and that such change was often non-incremental. It ends by proposing a model by which to illustrate the conditions under which regime change occurs in response to a shock.