The risk of Crohn's disease in relation to oral contraceptive use was evaluated in a hospital-based, case-control study of 57 women with Crohn's disease and 2189 controls with other conditions. The relative risk for oral contraceptive users compared with women who had never used these drugs was 1.9 (95% confidence interval 1.0-3.5). The magnitude of the relative risk estimate was related to the timing and duration of oral contraceptive use. For use within the year before admission to a hospital (recent use), the relative risk estimate was 4.3 (2.1-8.7); the estimate dropped to 1.2 (0.5-2.6) 4 yr after discontinuation of oral contraceptive use. The relative risk estimate for recent use that lasted greater than or equal to 5 yr was 8.0 (3.1-21). The findings are in accordance with earlier reports of an increased risk of Crohn's disease in oral contraceptive users.