During the fifteen year period 1969-1983, 493 patients with primary acute pancreatitis were admitted to Nottingham hospitals. The incidence of this disease increased from 75.1 per million per year for 1969-1976 admissions to 116.9 per million per year for 1977-1983 admissions. For both cohorts there were large statistically significant variations in the distribution of pancreatitis within the study area. The spatial distribution for both cohorts revealed that the highest incidence rates clustered in an area east of the city centre which is supplied by particularly "hard" water. The chemical composition of the domestic water supply may play a role in the manifestation of acute pancreatitis.