The hypothesis that a linear relationship exists between dose and induction of neoplasms is supported by data for humans. Under this hypothesis, g rad dosages to groups of individuals who have been followed, is used to calculate various neoplastic doses. Infants are shown to be more prone to radiation induced neoplasms than adults. It may be concluded that even though there are uncertainties in the data and in the hypothesis, the conservative approach to the irradiation of man will utilize these figures until the basic assumptions are disproved, or until more precise figures become available.