Exposures of a large population in the Denver area to plutonium and other radionuclides in the exhaust plumes from the Rocky Flats (nuclear weapons) plant date back to 1953. Anglo cancer incidence in 1969-1971 was evaluated in census tracts with and without contamination in the Denver area (1970 pop. 1 019 130). Cancer incidence in males was 24 percent higher, and in females, 10 percent higher in the suburban area (pop. 154 170) with most contamination nearest the plant, compared to the unexposed area (pop. 423 870), also predominantly suburban, which had virtually the same age-adjusted incidence rate for all cancer as the state. Excess cases of cancer were due to more cases than expected of leukemia, lymphoma and myeloma and cancer of the lung, thyroid, breast, esophagus, stomach and colon, a pattern similar to that observed in the survivors of Hiroshima and Nagasaki. The ratio of these cancers to all other cancer was 17.6 percent higher in males and 11.9 percent higher in females in the area near the plant. Cancer of the gonads, (especially of the testes), liver, and, in females, pancreas and brain contributed to the higher incidence of all cancer in areas near the plant.