The capacity to build nuclear weaponsknown as nuclear latencyis widely believed to be important in world politics. Yet scholarly research on this topic remains limited. This paper introduces a new dataset on nuclear latency from 1939 to 2012. It discusses coding procedures, describes global trends, and compares the dataset with earlier efforts to measure nuclear latency. We show that nuclear latency is far more common than nuclear proliferation: 31 countries developed the capacity to build nuclear bombs from 1939 to 2012, and only 10 of those states went on to acquire atomic arsenals. This paper provides one empirical application of the dataset, showing how the study of nuclear latency can contribute to our understanding of international conflict. We provide preliminary evidence that nuclear latency reduces the likelihood of being targeted in militarized disputes. Having the capacity to build nuclear weapons, therefore, may provide deterrence benefits that we usually associate with possessing a nuclear arsenal.