Crohn's disease is often described as a contraindication to the construction of a Kock pouch (KP), but a consensus opinion is less definite. One hundred consecutive patients with a KP were reviewed after a minimum follow-up time of 2 1/2 years. The 95 patients with inflammatory bowel disease were analyzed for serious complications. All eight patients in whom the diagnosis of Crohn's disease or inflammatory disease of indeterminate type was made suffered serious complications requiring resections of the pouch or continuing treatment. By contrast, of the 87 cases with ulcerative colitis, only 17 (20 percent) had complications, six of which were readily and simply corrected. Our findings suggest that Crohn's disease should continue to be regarded as a firm contraindication to the KP procedure. It should be actively sought out preoperatively, and it should be treated aggressively if it is discovered after surgery. If such a patient requires further surgery, the KP should be removed.