Serum phosphate levels were measured in a group of 78 patients admitted to hospital with a confirmed diagnosis of acute pancreatitis. Forty-seven (60%) of these patients developed significant hypophosphataemia (less than 0,8 mmol/l) within 4 days of admission. Serum phosphate levels were generally normal on admission, declined on the 2nd-5th days, and returned to normal within 3-14 days. A history of previous excessive alcohol intake was obtained from 42 patients (89%) in the hypophosphataemic group and from 28 (90%) in the normophosphataemic group. In view of the close similarities between the complications of acute pancreatitis and those of hypophosphataemia, including 'toxic psychosis', haematemesis, haematological disturbances, bone infarcts, respiratory failure, abnormal liver function and hyperglycaemia, it is suggested that at least some of these complications could be due to phosphate depletion. Phosphate replacement may be of benefit in their prevention.