[en] Two studies on Los Alamos workers exposed to plutonium have shown no increase in cancers of the lung, bone, and liver, three principal cancers of interest following plutonium deposition. A clinical study of 26 workers exposed 32 years ago shows no cases of cancer other than two skin cancers that were excised successfully. A mortality study of 224 workers, all persons with estimated deposition of 10 nCi or moe in 1974, showed no excess of mortality due to any cause. No bone or liver cancers were present, while one death due to lung cancer was observed as compared to an expected three cases. These negative findings on such small groups are not able to prove or disprove the validity of commonly used risk estimates as recommended in the 1972 BEIR and 1977 UNSCEAR reports, but the data do indicate that much higher risk estimates are not warranted