We investigated the association between medically diagnosed spontaneous abortions and occupational exposure to organic solvents. The study population was composed of women biologically monitored for solvents. The workers were classified into exposure categories on the basis of work description and the use of solvents as reported in the questionnaires, and on biological exposure measurements. The odds ratio of spontaneous abortion for solvent exposure, adjusted for potentially confounding factors, was significantly increased (2.2, 95% confidence interval [CI] = 1.2-4.1). The increase was most consistent among workers exposed to aliphatic hydrocarbons: the odds ratio for high exposure was 3.9 (95% CI = 1.1-14.2) and for exposed graphics workers 5.2 (95% CI = 1.3-20.8). The odds ratio was increased also among toluene-exposed shoe workers (9.3, 95% CI = 1.0-84.7). The results of the study support the hypothesis of a positive association between spontaneous abortion and exposure to organic solvents during pregnancy and suggest that exposure, especially to aliphatic hydrocarbons, increases the risk of abortion.