A cohort mortality study was conducted of all adult residents who ever lived in Uravan, Colorado, a company town built around a uranium mill. Vital status was determined through 2004 and standardised mortality analyses conducted for 1905 men and women alive after 1978 who lived for at least 6 months between 1936 and 1984 in Uravan. Overall, mortality from all causes (standardised mortality ratio (SMR) 0.90) and all cancers (SMR 1.00) was less than or as expected based on US mortality rates. Among the 459 residents who had worked in underground uranium mines, a significant increase in lung cancer was found (SMR 2.00; 95% CI 1.39-2.78). No significant elevation in lung cancer was seen among the 767 female residents of Uravan or the 622 uranium mill workers. No cause of death of a priori interest was significantly increased in any group, i.e. cancers of the kidney, liver, breast, lymphoma or leukaemia or non-malignant respiratory disease, renal disease or liver disease. This community cohort study revealed a significant excess of lung cancer among males who had been employed as underground miners. We attribute this excess to the historically high levels of radon in uranium mines of the Colorado Plateau, coupled with the heavy use of tobacco products. There was no evidence that environmental radiation exposures above natural background associated with the uranium mill operations increased the risk of cancer. Although the population studied was relatively small, the follow-up was long, extending up to 65 years after first residence in Uravan, and nearly half of the study subjects had died.