"This paper surveys trends and conclusions in federally sponsored studies of nuclear reactor safety and their implications for nuclear regulation. The paper finds that recent studies do not rule out the possibility of light water reactor accidents equal to or even larger in size than the 1986 Chernobyl accident. The probability of such an event"-"involving both core melt and prompt containment failure"-"is quite small, but the Nuclear Regulatory Commission's (NRC's) estimated probability of core melt is significantly higher. The paper reviews the NRC's use of these findings through a probabilistic cost-benefit framework, and it concludes that a greater and focused NRC commitment to risk reduction is justified." Copyright 1990 Western Economic Association International.