[en] A retrospective cohort mortality study was conducted among employees of the Oak Ridge National Laboratory. Since 1943, this facility has been the site of energy-related research, including uranium and plutonium recovery and radioisotope production. Historical follow-up conducted for the years 1943 to 1977 for 8681 white males who had been employed for at least one month during the period 1943 to 1972. Vital status was ascertained for 90 percent of the cohort. Standardized Mortality Ratios (SMRs) were computed to contrast the workers' mortality experience with that of the US white male population. The observed number of 1017 deaths from all causes was 74 percent of that expected, a finding indicative of the healthy worker effect and the relatively high socioeconomic status of the cohort. The SMR for all cancers was 0.75 (195 observed vs. 261.3 expected). Mortality deficits were seen for non-malignant diseases of all major organ groups and for all site-specific malignancies except prostate cancer (SMR = 1.13), leukemia (SMR = 1.16) and Hodgkin's disease (SMR = 1.28). None of the elevations was statistically significant. There were no consistent trends of cause-specific mortality with either external or internal radiation exposure levels