[en] Mortality among plutonium and other nuclear workers has been investigated to assess the effects of exposures to low levels of internal and external radiation. Standarized mortality ratios (SMRs) for white male workers employed at least two years from 1951 through 1977 were significantly lower than expected for all causes, all cancers, cancers of the respiratory system, and lung cancer. Benign neoplasms, all of which were intracranial tumors, were significantly elevated. No bone cancers were discovered and other radiogenic cancers did not differ significantly from expectation. Duration of employment and latency did not affect these results. SMRs for a subcohort of plutonium exposed workers were significantly low for all causes of deaths and all cancers. Estimates of relative risk for workers exposed to 2 or more nCi compared to unexposed workers were not significantly higher or lower than unity. These findings do not support the hypothesis of increased mortality among plutonium and other nuclear workers. The excess for benign and unspecified intracranial tumors is not consistent with previous studies on radiation induced brain tumors in terms of latency and exposure levels