Mucinous ductal ectasia (MDE) is an uncommon disease characterized by a patulous duodenal papilla extruding mucus, and a pancreatogram showing dilation with amorphous filling defects, communication of the mass with the pancreatic duct, the mass usually being located in the head of the pancreas. We have recently treated three men and three women, mean age 66 years, with MDE. All had abdominal pain, while 33% had the clinical picture of pancreatic insufficiency. Three patients had recurrent pancreatitis, and three had biliary obstruction. Endoscopic retrograde cholangiopancreatography and imaging studies showed a patulous papilla draining mucus in six, pancreatic duct dilation in six, filling defects in six, and communication between the cystic mass and the pancreatic duct in five. A distinct finding not previously reported was a separate pancreatic and biliary orifice in two. Three patients had cancer, two cases being metastatic and one being found at surgery (not suspected preoperatively). Therapy included endoscopic biliary drainage in two, surgery in three, while one refused surgery. Of the operated patients, two underwent resection, one of whom had benign disease and the other cancer; both patients are doing well 14 and 32 months after surgery, respectively. One patient underwent pancreatojejunostomy without symptomatic relief, and developed cholangitis 18 months after surgery that was successfully treated with endoscopic drainage. The other two patients treated with biliary drainage died one and 13 months later, respectively. We conclude that MDE has characteristic pancreatographic and endoscopic findings, and that it is commonly associated with malignant degeneration. Surgical resection is the treatment of choice, since MDE is premalignant, and surgery may be curative when the malignancy is resectable.