Two groups of patients admitted with a first attack of acute pancreatitis are reviewed. The first group, consisting of 105 patients, was admitted between 1968 and 1969; the second group of 204 patients was admitted between 1974 and 1975. These groups were compared with one of 454 patients admitted between 1956 and 1960 whose details were published earlier by our unit (Edlund et al., 1968). The aim of this study was to determine whether the incidence of factors associated with pancreatitis within the population of the city of Göteborg had changed in the 20-year period. In the 1956--60 group gallstone disease was the main associated factor (68 per cent), but in the later groups alcohol-induced pancreatitis assumed the leading role (68 and 66 per cent respectively). Alcohol-induced pancreatitis tended to occur at a younger age than gallstone pancreatitis. Thirty-one per cent of 449 patients admitted with an acute attack of alcoholic pancreatitis in the two last periods of study had had previous attacks.