Pancreaticobiliary diversion is a surgical procedure undertaken for obesity. It consists of a distal gastrectomy with a long Roux-en-Y reconstruction, the enteroenterostomy being placed 200 cm distal to the gastroenterostomy and 50 cm proximal to the ileocaecal valve. Three intestinal limbs are recognized: (a) the alimentary loop from the gastroenterostomy to the enteroenterostomy; (b) common loop from the enteroenterostomy to the ileocaecal valve and (c) pancreaticobiliary loop from the duodenum to the enteroenterostomy. The radiological findings in 15 pancreaticobiliary diversion patients with small bowel obstruction were reviewed (15 plain abdominal radiographs, 13 ultrasound (US), 8 CT) and compared with 20 plain abdominal radiographs, 10 US, and 10 CT studies performed for other causes in patients with pancreaticobiliary diversion and 15 CT scans from non-operated patients. After pancreaticobiliary diversion the pancreaticobiliary loop was completely air-free. In the patients operated on more than 1 year previously, alimentary and common loops were significantly larger than the pancreaticobiliary loop and small bowel loops of non-operated subjects. Obstruction of the pancreaticobiliary loop arrests only the flow of pancreaticobiliary secretions with non-specific clinical findings. Plain abdominal radiographs were not diagnostic in all but two cases with radiographically detectable dilated fluid filled loops. Air-fluid levels were never apparent. US and CT showed markedly dilatated intestinal loops and duodenum. Obstruction of the alimentary and common loops presented with symptoms, clinical signs, and radiological findings more typical for bowel obstruction in intact subjects.