Regional enteritis involves the duodenum more commonly than has been suspected. The demonstration of tubular narrowing of the antrum, pylorus, duodenal bulb, and second portion of duodenum is almost pathognomonic of the disease. Any inflammatory change of the duodenal loop in the absence of clinical pancreatitis warrants consideration of the diagnosis of regional enteritis and complete evaluation of the gastrointestinal tract. Patients with duodenal involvement will usually have the more easily recognizable changes in the small bowel and/or colon.