Thirty patients suffering from chronic alcoholic pancreatitis (18 calcified) were entered into a study of exocrine and endocrine pancreatic function based on two maximal stimulation tests, namely the secretin-cerulein test and the glucagon test with serum assays of C peptide. The glucagon test was also performed in 19 control subjects. In addition, 10 chronic pancreatitis patients and nine controls were subjected to an oral glucose tolerance test (OGTT) with serum insulin determinations. C peptide basal values were decreased only in patients with severe pancreatic exocrine insufficiency (P less than 0.001), while delta C peptide values were also reduced in patients with moderate exocrine insufficiency (P less than 0.001). Lipase output correlated very well with delta C peptide values (P less than 0.001). While serum insulin levels during OGTT and C peptide basal values showed no significant differences between the chronic pancreatitis and control groups, delta C peptide values were significantly reduced in chronic pancreatitis patients (P less than 0.02). Both endocrine and exocrine function are impaired in chronic pancreatitis, as demonstrated by maximal tests, even in early stages of the disease.