Solvents are extensively used in pesticide formulations. This study concerns the solvents notified to the Italian Registry of Pesticides, which has information on approximately 8000 pesticide formulations. Solvents with evidence of carcinogenicity in humans or animals, including benzene, chloroform, carbon tetrachloride, 1,2-dichloroethane, 1,4-dioxane, and 2-nitropropane, have been notified for use in pesticides. Exposure to such solvents could partly explain some of the reported excesses of leukemia and non-Hodgkin's lymphoma among farmers.