In ten patients, operated jejunoileostomy and ileocolostmy because of longstanding obesity resistant to conventional therapy, roentgenological examinations of the small bowel were performed before and after the operation. Seven patients were examined preoperatively, and all were investigated at least twice during a period from 1 to 38 months postoperatively. Preoperatively, the passage time pylorus-cecum was 80-270 min, and postoperatively, it varied between 1 and 30 min. There was no tendency to slowing of the gastrointestinal passage with time. Immediately postoperatively, the patients had 6 to 12 loose stools daily. At investigations performed 6-38 months after the operation, the stool frequency had diminished to 1-4 a day, and the patients had lost 21 to 98 kg in weight. Roentgenologically, an increased thickness of the mucosal folds of the small bowel could be demonstrated in 9 of the 10 patients. The results suggest that in patients with jejunoileostomy, the gastrointestinal passage time is decreased. The bowel function tends to normalize with time, but the passage time remains shorter than normal. Compensatory changes in the intestinal mucosa occur.