This chapter identifies the track record of the regime – its recent history of compliance – as a key driver of the decisions of states to abide by their nonproliferation commitments. The argument begins with the simple idea that the regime is based on a fundamental bargain among member states: each member is willing to comply only so long as others do. When states join the regime, they do so with some expectation about its performance—the extent to which other states ultimately will abide by their commitments. There is often significant uncertainty surrounding this expectation, however, and new information about the performance of the regime will help resolve uncertainty and influence compliance. The track record of the regime provides the best source of such information. As time passes with few violations, states will in turn be more likely to comply themselves. Evidence of rampant noncompliance, on the other hand, will make states more likely to cheat. This logic is reflected in Japan’s consideration of nuclear weapons development over the years and is supported by statistical tests using data on nuclear weapons programs by NPT members.