The effect of cigarette smoking on recurrence (defined in this study as the need for repeat surgery) in patients who had previously required surgery for Crohn's disease was assessed in a historical cohort of 174 patients. Mean follow-up was 10.8 yr. The 5- and 10-yr recurrence rates were 28% and 56%, respectively. Five- and 10-yr rates were significantly different for smokers (36%, 70%) and nonsmokers (20%, 41%). When patients were stratified by gender, the increased risk was more apparent in women (odds ratio 4.2, 95% confidence interval 2.0-4.2) than in men (odds ratio 1.5, 95% confidence interval 0.8-6.0). Evidence for a dose-response relationship could be identified in women but not men. Cigarette smoking may not only be a risk factor for development of Crohn's disease but also may influence disease activity following surgery.