We determined the types of pancreatobiliry ductal anatomy in 58 chronic alcoholic patients with and without pancreatitis at ERCP. Twenty-four of 28 patients (86%) with pancreatitis had separately opening common bile ducts and pancreatic ducts, while only six of 30 patients (20%) without pancreatitis had this finding. We conclude that a separate channel configuration is an inherited predisposing factor to alcoholic pancreatitis. As both chronic alcohol ingestion and separately opening bile and pancreatic ducts have been associated with ductal epithelial hyperplasia, the pathogenesis of alcoholic pancreatitis may be hy way of duct obstruction produced by cell hyperplasia.