Pancreas divisum is a congenital variant of pancreatic duct drainage in which the dorsal duct dominates, most likely due to the failure of the two independent pancreatic ductal systems to fuse embryologically. Although 5 to 10 percent of the population have this congenital variation, few demonstrate symptoms related to their pancreaticobiliary ductal systems. However, patients may present with symptoms referable to this system, and the diagnosis is difficult. In this series, endoscopic retrograde cholangiopancreatography with cannulation and radiographic injection of the dorsal duct demonstrated this abnormality in 30 of 32 patients, and results of morphine-prostigmine testing were positive for symptoms, chemical enzyme elevation, or both in three fourths of the patients tested, but other maneuvers were not as helpful. The surgical approach has been to perform a sphincteroplasty of both the main and accessory ampullas and to excise the gallbladder when it is present. Pathologic study of the gallbladders showed nearly all of them to have been diseased, whereas histologic study of the ampullas was not as conclusive. In general, this condition should be suspected as part of the postcholecystectomy syndrome or in patients who present with idiopathic pancreatitis and whose conditions cannot be identified by all other diagnostic methods. Preoperative screening may be carried out with noninvasive techniques such as the morphine-prostigmine test, or by use of the secretin-stimulated ultrasonographic visualization of the ductal system. The primary tool for making the diagnosis is endoscopic retrograde cholangiopancreatography. The goal of surgical treatment should be the opening of the main and accessory ducts, since this offers the best chance for long-term relief of the patient's symptoms.