Pathophysiology of the sphincter of Oddi--or sphincter of Oddi dysfunction--manifests as either a biliary-type pain syndrome or recurrent pancreatitis. Imaging studies are unreliable, and direct endoscopic manometry is used to diagnose this entity. Milwaukee biliary classification, in addition to manometry, helps guide therapy. Endoscopic sphincterotomy in selected patients achieves permanent relief of symptoms. Endoscopic therapy for recurrent pancreatitis is still experimental.