Between 1977 and 1986, 92 patients with Crohn's disease (53 females and 39 males, average age 32 years at diagnosis) were admitted for a total of 158 hospital stays at the St. Claraspital, Basel. In 71 cases the diagnosis was based on one or more of radiologic and endoscopic evaluation and/or operative findings. In 4 cases diagnosis was based solely on clinical findings and in the remaining 17 the original diagnostic workup could not be evaluated retrospectively. 65% of cases were histologically proven, while the rest of the patients were either not biopsied or biopsy yielded inconclusive results. Crohn's disease was located simultaneously in the small and large bowels in 41 patients, in the small bowel only in 23 (25%) and in the large bowel only in 20 (22%). The remaining localizations were either proximal GI tract or anal region only. Surgery was performed a total of 65 times in 44 of the 92 patients (48%), the most frequent procedures being ileocecal resection and surgical treatment of perianal fistulas and abscesses. Accordingly, the main indications for surgery were perianal complications (37%) and stenotic bowel lesions (29%). The resection rate was higher in ileal (35%) than in colorectal (25%) involvement. The 3 rectal amputations eventually necessary were all in patients with anorectal involvement.