SUMMARY A prospective study of 116 patients with acute pancreatitis included routine screening for evidence of viral infection. Five patients (all female) exhibited significant rising antibody titres to Coxsackie B or mumpsvirus, while none of the remaining 111 patients did. Diarrhoea was a prodromal feature of the pancreatitis in those patients with evidence of viral disease. Screening patients with acute pancreatitis for Coxsackie B and mumpsvirus infections is worthwhile in the identification of aetiological factors and may minimise protracted biliary investigations. The incidence of 'idiopathic' acute pancreatitis in this study was 5-2% (six patients).Recent prospective studies of acute pancreatitis (Ranson et al., 1974;Imrie and Whyte, 1975) have indicated that the group of patients considered to have 'idiopathic' acute pancreatitis represent no more than 12% of the total cases. The two common aetiological factors associated with acute pancreatitis in over 75 % of patients are biliary disease and excess alcohol ingestion (Ranson et al., 1974;Howes et al., 1975;Imrie and Whyte, 1975). Hyperlipoproteinaemia, hyperparathyroidism, steroids, hypothermia, and pancreatic neoplasm are aetiological factors in a small percentage of cases.