The purpose of the study was to investigate mortality in a cohort of 2,514 white males employed in a uranium processing facility between 1942 and 1966 to evaluate: 1) mortality compared to the U.S. population, and 2) the relationship between external ionizing radiation and cancer and other diseases of the respiratory, digestive, genitourinary, and lymphatic systems. Standardized Mortality Ratios (SMRs) were calculated for 56 causes of death. Annual external radiation doses were obtained from individual film badge readings. Poisson trend test statistics were computed using time-dependent cumulative doses. dose-response estimates with likelihood based confidence intervals (CIs) were calculated using a stratified excess relative risk model. Through 1993, 1056 deaths were ascertained. Population dose from external radiation was 120 sieverts. Cumulative individual doses had a mean of 47.8 mSv and median of 15.3 mSv. SMR with a 95% CI was 0.92 (0.86, 0.97) for all causes and 1.10 (0.98,1.23) for all cancers; respiratory diseases, chronic nephritis, and lymphatic cancers were significantly elevated. Trend tests revealed a statistically significant increase of kidney cancers based on 11 deaths (p=0.02) with relative risk estimate per Sv of 12.9 with a 90% CI (1.4,67.6). The only disease of a priori interest with evidence of exposure related effects was kidney cancer. While this appears to be related to exposure to radium and its daughters resulting from high grade uranium ore processing prior to removal of the radium component, it must be considered provisional since external radiation exposure may be a surrogate for internal radiaiotn dose or chemical exposures which were not considered in this study.