rved INTRODUCTION Fallout from nuclear weapons tests has been by far the principal man-made source of radioactive environmental contamination. About 340 nuclear detonations in the atmosphere, by all nations testing, have been announced. million tons pels irea The tstal energy release has been about 511 (MI) equivalent of TNT with the USSR tests accounting for about 70 percent of the total.t- Included in this total energy release is about 193 million tons of fission - the process that creates the radioactive fission products present in fallout.!- (Two hundred million tons of TNI energy equivalent would produce about 12 tons, by unt weight, of fission product debris.) The discussion that follows in Section I. attempts to summarize an enormous amount of data and to present some evaluation of the estimated radiation exposures to persons from fallout. The remaining Sections deal with other health aspects of nuclear weapons testing. The information presented herein is intended to provide some answers to three basic questions concerning the testing of nuclear weapons: 1. What are the problems and possible risks associated with tuclear weapons testing? 2. What are the data concerning effects from past tests? 3. What do these data mean - how serious are the possible risks? (Graphics No. 1 (See list at end of document) iii.