We studied 267 consecutive Italian patients (146 male, 121 female) with Crohn's disease. Median time from the first symptom to diagnosis at our center was 21 months (range 1-372), whereas median follow-up from the first visit was 38 months (range 1-180). The disease affected the small bowel in 93 (35%) cases, the ileum and colon in 76 (28%), and the colon in 98 (37%). Forty-nine percent of the patients underwent major abdominal surgery for the disease at least once. The cumulative probability of abdominal surgery was 36% and 55%, 60 and 120 months after the onset of symptoms, respectively. Univariate analysis indicated that patients with colon involvement (p less than 0.0001), those with a longer interval between first symptom and diagnosis (p less than 0.0001), and those at an older age at diagnosis (p less than 0.0003) had a significantly greater probability of escaping abdominal surgery. The interval between first symptom and diagnosis, the site of disease, and the age at diagnosis were confirmed as risk factors for surgery, in decreasing order of importance, by multivariate analysis with Cox's proportional hazard model. A prognostic index for first operation based on these variables is proposed.