Twenty-six white male workers who did the original plutonium research and development work at Los Alamos have been examined periodically over the past 50 y to identify possible health effects from internal plutonium depositions. Their effective doses range from 0.1 to 7.2 Sv with a median value of 1.25 Sv. As of the end of 1994, 7 individuals have died compared with an expected 16 deaths based on mortality rates of U.S. white males in the general population. The standardized mortality ratio (SMR) is 0.43. When compared with 876 unexposed Los Alamos workers of the same period, the plutonium worker's mortality rate was also not elevated (SMR = 0.77). The 19 living persons have diseases and physical changes characteristic of a male population with a median age of 72 y (range = 69 to 86 y). Eight of the twenty-six workers have been diagnosed as having one or more cancers, which is within the expected range. The underlying cause of death in three of the seven deceased persons was from cancer, namely cancer of prostate, lung, and bone. Mortality from all cancers was not statistically elevated. The effective doses from plutonium to these individuals are compared with current radiation protection guidelines.