We studied serum elastase 1 concentrations in patients with pancreatic disease to assess its diagnostic value and compare its sensitivity and specificity with that of amylase and pancreatic isoamylase. Markedly raised concentrations of elastase 1 were found in all twenty-nine patients with acute pancreatitis (amylase was elevated in all but three and pancreatic isoamylase in all but one). Serial measurements of the three enzymes in acute pancreatitis showed that elastase remained elevated longer than amylase and pancreatic isoamylase. The majority of chronic pancreatitis patients studied during a painful relapse (16 out of 21, 76 per cent) had elastase concentrations above the upper normal limit. Amylase and pancreatic isoamylase were elevated in 11 (52 per cent) and in 13 (62 per cent), respectively. Most patients with chronic pancreatitis studied during clinical remission (39 out of 43) had serum elastase levels either within (n = 24) or below (n = 15) the control range. The latter had severe exocrine pancreatic insufficiency and steatorrhoea. In carcinoma of the pancrease, 20 out of 32 (63 per cent) had abnormal serum elastase concentrations; 16 were higher and 4 lower than the control range. Amylase was abnormal in 10 (31 per cent) (8 high, 2 low), and pancreatic isoamylase was abnormal in 16 (50 per cent) (11 high, 5 low). In 46 control patients with non-pancreatic abdominal pain, serum elastase concentrations were not significantly different from those in healthy controls. Elastase was slightly raised in two, whereas amylase and pancreatic isoamylase were elevated in seven and eight, respectively. We conclude that serum elastase 1 is a highly sensitive and specific indicator of pancreatic disease.