Crohn's disease confined to the appendix is a rare entity, less than 50 cases having been reported. The present study reports on another 12 cases representing 6 per cent of all 194 patients operated upon for Crohn's disease in a total, unselected series. The indications for surgery were appendicitis in eight patients, appendiceal abscess in two, suspected pyosalpinx in one, and an ovarian cyst in one. The appendices were in all cases strikingly enlarged. Giant-cell granulomas, without microabscesses were detected in all but one patient. Two patients had early septic postoperative complications. Fistulization from the cecum did not occur. The median observation time after operation was 13.8 years. Since none of the patients had further manifestations of the disease, it is concluded that patients with Crohn's disease confined to the appendix have a favorable prognosis.