Even since its description approximately 100 years ago, the sphincter of Oddi has been surrounded by controversy. First, whether it indeed existed, second, whether it had a significant physiological role in man and more recently whether abnormalities in its function give rise to a clinical syndrome. Data from animal and human studies, using sensitive techniques, have helped define the physiological role of the sphincter of Oddi, and more recent studies are determining the factors which control sphincter of Oddi function. These studies support Oddi's original description that the sphincter has a major role in the control of flow of bile and pancreatic juice into the duodenum, and equally importantly helps prevent the reflux of duodenal concents into the biliary and pancreatic ductal systems. The controversy of whether abnormalities in sphincter of Oddi motility result in clinical syndromes has not been totally resolved. Part of the difficulty has been inability to document normal and hence abnormal function of the sphincter. With the emergence of endoscopic biliary manometry as a sensitive and reproducible technique, however, the motility of the human sphincter of Oddi has come under closer scrutiny and allowed definition of possible disorders. We have used the term sphincter of Oddi dysfunction to define manometric abnormalities in patients who present with signs and symptoms consistent with a biliary or pancreatic ductal origin. Based on the manometry, we have subdivided the dysfunction into two groups; a group characterised by a stenotic pattern - that is, raised sphincter basal pressure - and a second group having a dyskinetic pattern - that is, paradoxical response to cholecystokinin injection, rapid contraction frequency, high percentage of retrograde contractions, or short periods of raised basal pressure. It is apparent from the mamometry but also from the clinical data that the patients are a heterogeneous group and thus any therapy would need to be tailored for each patient and abnormality. The most recent therapeutic data suggest that patients with the stenotic pattern on manometry respond to division of the sphincter, however, those patients with the dyskinetic manometric pattern show no significant effect after sphincterotomy. Further prospective trials evaluating therapeutic options are under way and their results are eagerly awaited.