To estimate the diagnostic value of elastase output in the duodenal aspirates during a pancreozymin secretin test, elastase as well as amylase, chymotrypsin, trypsin, and lipase was determined in 46 controls and 61 patients with various disease. The elastase output decreased significantly in chronic pancreatitis (mild exocrine insufficiency 13 and advanced eight), pancreatic cancer (n = 10), and liver cirrhosis (n = 14) when compared with the controls. The outputs of the four other enzymes also decreased in chronic pancreatitis and pancreatic cancer, not in liver cirrhosis. Low elastase output was found in four of 13 chronic pancreatitis patients with mild exocrine insufficiency, whereas low outputs of the other enzymes were observed in only one or less of the 13. The ratio of elastase to amylase alone was significantly lower in the pancreatic diseases. The results suggest that elastase is the most susceptible enzyme to pancreatic dysfunction and that its output and its ratio to amylase output provide a valuable index to assess the enzyme secretory capacity in the pancreatic diseases.