Peutz-Jeghers syndrome is characterized by hamartomatous polyposis of the small and large bowel and mucocutaneous pigmentation. The authors describe a 9-year-old girl with small bowel obstruction related to duodenal intussusception caused by polyposis in the fourth portion of the duodenum. Operative reduction of the intussusception and excision of the polyps were performed, at which time the pancreas appeared to have mild pancreatitis. A liver biopsy specimen showed mild portal fibrosis and ductal proliferation. The patient did well postoperatively, but later presented with symptoms consistent with biliary obstruction. Percutaneous transhepatic cholangiography showed pancreatic and biliary duct dilatation as well as obstruction of the common bile duct, which extended into the left upper quadrant. Exploration showed ampullary obstruction several centimeters proximal to the line of resection. Sphincteroplasty was performed. The postoperative course was uncomplicated. The authors conclude that Peutz-Jeghers syndrome with polyps in the duodenum can markedly distort duodenal and ductal anatomy and can lead to ampullary obstruction.