The clinical course of Crohn's disease in 131 patients was studied for a mean period of 4.2 +/- 3.2 years. The clinical activity of the disease, expressed as percentage of patients per year in an active phase, is high in the first year (70.2 percent) and progressively decreases during subsequent years (25 percent after seven years). The percentage of patients who needed steroid treatment is high during the first year (68 percent) and falls to 19 percent after seven years. An operative risk rate of 54 percent was registered, with a probability of reoperation equal to 34 percent. Clinical relapse after the first surgery occurred in 70 percent of cases. The registered mortality was 6.9 percent, with a ratio of 6 to 1 between observed and expected mortality. In conclusion, the disease, while showing a tendency to reduce its activity over the years, is burdened by a risk of surgery and mortality which progressively increases with time.