Nine-Year Mortality Experience in Proton-Exposed Macaca mulatta

Macaca mulatta exposed at 2 yr of age to proton irradiation have been observed for mortality and latent effects since 1964. This report of progress covering the first 9 yr postexposure shows an interesting occurrence of neoplasia in the 55 MeV proton-exposed animals and an increased incidence of endometriosis in whole-body penetrating proton exposures. For doses of 400 rad and less, no significant deviation from control mortality is apparent, 9 yr postexposure.