To identify potential risk factors that influence postoperative recurrence rates of Crohn's disease, the postoperative recurrence-free survival of 93 patients who underwent their first resections at The Mount Sinai Hospital between 1964 and 1973 has been examined. Features analyzed individually and jointly were age, sex, anatomic location, operative procedure, and preoperative disease duration. In patients with Crohn's colitis, recurrence rates appeared somewhat lower among 11 patients with ileostomy than among 5 patients with anastomosis. In the entire series, recurrence rates were lowest in patients with longest preoperative durations (p = 0.02). This same tendency was especially marked among the 68 patients without ileostomies (p = 0.005). Likewise, among the 38 patients with ileitis, the relative risk of recurrence was significantly lower for those with disease duration exceeding 10 yr (p = 0.01). Relative risk of recurrence in the entire series for patients with 2-yr duration was 1.5 compared with those who had 10-yr duration. This inverse association between preoperative disease duration and postoperative recurrence rate may reflect persisting differences between inherently more aggressive versus more indolent forms of Crohn's disease.