Recent studies described an increased concentration of protein and calcium in association with a decreased concentration of citrate in pancreatic juice of patients suffering from chronic pancreatitis. These secretory changes may be of importance in the pathogenesis of chronic pancreatitis. The present study investigates pancreatic juices of 18 patients without pancreatic disease and 12 patients in an early phase of chronic pancreatitis in order to detect changes of the exocrine function of the pancreas in an early stage of the disease. In all persons the pancreatic juice was collected by endoscopic cannulation of the main pancreatic duct after i.v. stimulation with secretin and pancreozymin. The outputs and concentrations of protein, calcium and citrate were estimated. All of these parameters did not differ in control subjects and patients with chronic pancreatitis by univariate statistical analysis. However, a multivariate analysis detects differences in the biochemical composition of the secretions of controls and patients with chronic pancreatitis (efficiency of discrimination = 100%). Both in controls and in patients with chronic pancreatitis two calcium fractions were found after secretin stimulation: one secretory protein-associated fraction of 94 nmol calcium/mg protein and a protein-independent calcium fraction of 0.248 mmol/l, which diffuses paracellularly from the interstitium into the pancreatic juice. The results show that the secretory function of the exocrine pancreas is already disturbed in an early phase of chronic pancreatitis, whereas an increased lithogenity of the pancreatic juice cannot be detected.