In most countries primary acute pancreatitis is a rare disease. However, its incidence has been increasing for several decades and many patients do not survive their first attack. During the 15 years (1969-1983) 493 patients with the disease were admitted to Nottingham's two District General Hospitals. The geographical distribution of the disease within the study area was determined using 62 electoral wards and two patient cohorts namely 214 1969-1976 admissions (1971 census base) and 279 1977-1983 admissions (1981 census base). The incidence of the disease increased from 27 per annum to 40 per annum in the two cohorts. Most of the alcohol associated patients (18 first cohort: 38 second cohort) were young or middle aged males. For gallstone and 'non-gallstone' associated groups the incidence rose sharply with increasing age for both sexes. For both cohorts there were large statistically significant variations in the distribution of pancreatitis within the study area. Moreover, the spatial distribution was very similar for both cohorts with most of the highest rate wards clustering in a U-shaped area east of the city centre. Investigation of environmental factors suggested that this high-rate area coincides with the region served by the Burton Joyce domestic drinking water supply. Examination of the residential histories of the 493 patients showed that 25.6% had moved home less than five years prior to their first attack. Analysis of these moves confirmed that many patients had moved to suburban areas from two major inner city housing renewal schemes located within the high-rate Burton Joyce water supply area. Re-calculation of incidence rates of pancreatitis by former address for the six water supply areas established that only the Burton Joyce area had significantly high numbers of cases for both cohorts.