###### 2016 Distinguished Morton L. Mandel Annual Public Lecture **The Comprehensive Nuclear-Test-Ban Treaty at 20: Prospects for Ratification and the Enduring Risks of Nuclear Testing** Twenty years after the signing of the Comprehensive Nuclear-Test-Ban Treaty (CTBT) and creation of its accompanying organization, the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO), the CTBT remains extremely relevant in the context of nuclear proliferation, deterrence, testing, and more. Yet challenges also remain that impede the ratification of the treaty and its entry into force.