Experimental work in mice and dogs at such low body burden levels is incomplete, but at somewhat higher levels of Sr*® in mice the curve for bone tumor production is steeply sigmoidal in nature, in other words, very few if any bone sarcoma will result. 6 SUMMARY 1. Ihave attempted to review for you in an objective way the best information now available on the possible cost to society of the privilege of making use of atomic energy. 2. The estimate for the genetic cost in terms of gene mutations is based on a wealth of scientific data and while not absolutely proven the burden of proof should lie with those who question it. 3. The basis for the estimate of the upper limit for the leukemia cost is still in the realm of hypothesis though it must be taken account of in computing a possible maximum costof nuclear energy. 4, Estimates of the cost in terms of shortening of the average life span but exclusive of genetic effects as they may affect the life span of future generations are based on good data from experiments in animals exposed to dose increments of several roentgens. Whether there is any effect on life span at very low dose rates is not known. 5. The cost estimates discussed, even including the estimate for the ultimate genetic cost which is at least an order of magnitude greater than the highest cost estimates for leukemia are well below our present day experience with accidental deaths which is admittedly higher than need be. 6. All of these estimates assume that there will be no further advancesin the biological sciences with respect to the prevention and treatment of leukemia and cancer in general, and in our ability to counteract or protect against the mutagenic effect of ionizing radiations. 7 CONCLUSION Atomic energy like the other great technological advances is bound to exact some price of the society which makes use of it whether in peaceful pursuits or in its national defense effort. Our present knowledge of the hazards of radiation though incomplete is greater than for any other general environmental hazard. It is for the radiobiologist to continue to define the cost in more and more precise terms while it is up to society to decide whether the price is acceptable, and if the answer is in the affirmative, it must make certain that the cost is kept to a minimum. 281