In some cases of acute pancreatitis no cause can be identified. An etiologic role of Yersinia enterocolitica type 3 was suggested in two previous reports. A case is now presented which supports this hypothesis by simultaneity of reactive phase of yersiniosis and an acute attack of pancreatitis of otherwise unknown cause. Although the coincidence may have been fortuitous, the pattern common to this and the earlier published cases suggests that it may yield a further clue to an etiologic understanding of acute pancreatitis.