This study investigated the risk of lung cancer in regards to protracted occupational exposure to reprocessed uranium compounds. Two thousand seven hundred and nine male workers employed at the AREVA NC uranium processing plant between 1960 and 2005 in France were included in the cohort. Historical exposure to reprocessed uranium compounds classified by their solubility type was assessed on the basis of the plant's specific job-exposure matrix. Cox proportional hazard models adjusted for attained age, calendar period, and socioeconomic status were used to estimate relative risks in regards of each type of uranium compound. The relative risk of lung cancer tended to increase with decreasing solubility of reprocessed uranium compounds. The highest-though not statistically significant-relative risk was observed among workers exposed to slowly soluble reprocessed uranium dioxide. This study is the first suggesting an increasing risk of lung cancer associated with exposure to reprocessed uranium. Our results are consistent with data from experimental studies of biokinetics and the action mechanism of slowly soluble uranium compounds, but need to be confirmed in larger studies with more detailed dose-response analyses.