A case-control interview study of 125 adult patients with acute leukemia and 125 controls matched with respect to age (-+ four years), sex, and residence was carried out in central Sweden during the period from September 1980 to May 1983. Their history of organic solvent exposure is described. A significant overrisk of developing acute leukemia was found when comparison between patients and controls revealed a difference in the solvent exposure rate, which was significantly higher in patients than in controls, with an estimated odds ratio (OR) of 4.9,95% CI (2.2 to 12.1). The most frequently exposed profession, painters, exhibit a relative risk of 13 (2.0 to 554). These results suggest that an etiologic relationship exists between organic solvent exposure and the development of acute leukemia in man.