The association between oral contraceptive (OC) use and the risk of uterine fibroids was analyzed in a case-control study conducted between 1986-1990. The subjects were 390 patients under 55 years of age with histologically confirmed fibroids and 1136 controls in hospitals for a spectrum of acute conditions (other than gynecologic, hormonal, or neoplastic) apparently unrelated to OC use. A total of 78 cases (20%) and 200 controls (18%) reported OC use. Compared with never-users, the multivariate relative risk for ever-users was 1.1 (95% confidence interval [CI] 0.8-1.5). No direct relationship emerged with duration of use, the estimated relative risk being 1.3 (95% CI 0.9-2.0) in users of OCs for less than 3 years and 0.8 (95% CI 0.5-1.3) in users for 3 years or more. The risk of fibroids was apparently (though not significantly) greater with longer recency of use: The estimated relative risks were 0.9 and 1.5, respectively, in women reporting last OC use less than 10 years before and 10 or more years before diagnosis of the disease. No relationship emerged with latency of use. There was no noteworthy interaction regarding risk of fibroids between OC use and potential covariates. These findings suggest that fibroids are unrelated to the use of OCs.