One hundred fifty-two of 399 Crohn's patients (38 percent) diagnosed over 20 years, who lived within a geographically defined area at the time of diagnosis, underwent at least one operation. One hundred seventy-one resections were performed in 160 operations during a mean follow-up of 60 months. Forty-eight percent of patients had undergone their first resection within 10 years of diagnosis, and 39 percent of these had undergone a second resection within 10 years of the first. There was no difference between smokers and nonsmokers in the timing of their surgery.