What danger does ballistic missile proliferation pose, and what can be done to control it? Although the problem has become a prominent concern of the post-cold war world, it remains notoriously difficult to understand and deal with. This book assesses the problem from the broader perspective of the political and technical transformations of the 20th century. It draws on the author's experience as a proliferation analyst to explain the most controversial aspects of the global spread of long-range rocketry. The picture that emerges reveals an idiosyncratic problem, shaped by unique characteristics in every country where it is in evidence but also guided by strong general rules. By illuminating the key factors behind ballistic missile proliferation this study helps to explain why some of the most alarming regional rocketry projects have simply disappeared, while others make steady progress.