The double duct sign, defined as an abnormality of both the pancreatic duct and the contiguous part of intrapancreatic common bile duct, was found in 52 of 1180 patients studied by endoscopic retrograde cholangiopancreatography. Thirty patients were proved to have pancreatic malignancy and 22, benign pancreatic disease. Specific ductal characteristics found to indicate a malignant process were ductal obstruction, especially of the common bile duct, close proximity of the biductal lesions, a short stenotic segment of the common bile duct removed from the papilla, an abrupt, irregular transition from normal to stenotic or obstructed duct. Ductal characteristics suggesting a benign process were long length of common bile duct stenosis, calcium deposits, pseudocyst formation, and ectasia of pancreatic ductal branches central to the main duct lesion. This analysis indicates that the double duct sign per se is not disease specific, but when other ductal characteristics are assessed as a component of this finding, the ability to differentiate benign from malignant pancreatic disease is enhanced.