A method is presented for estimating the risk to the public from an underground Plowshare detonation, with a sample application to a hypothetical gas storage experiment. The method considers the probability of fission-product release as well as the frequencies of various wind and weather conditions. The fission-product release vs probability relationships were determined by a statistical analysis of applicable Nevada Test Site data, using a multivariate discriminate analysis technique. These relationships may be applied to most Plowshare underground engineering applications with the exception of those in media having formation pressure, such as natural gas stimulation. Results of the sample application indicate that the risks to the public from a Plowshare detonation are very small and that consideration should be given to executing experiments without planning for specific weather conditions.