One gram N-benzoyl-L-tyrosyl PABA was orally administered to 24 controls, 15 patients with chronic exocrine pancreatic disease, 13 patients after an attack of acute pancreatitis, two patients with gluten-sensitive enteropathy, and 10 patients with biliary tract disease, peptic ulcer, or other pathology of the gastrointestinal tract. In the presence of chymotrypsin, PABA is split from the peptide and excreted in the urine. The amount of PABA excreted serves as a parameter of exocrine pancreatic function. In 51 patients, exocrine pancreatic secretion was also assessed by the Lundh test. In the control group a mean of 59-6 +/- 12-2% (mean +/- 2 SD) of the peptide-PABA was excreted over a period of six hours. PABA excretion in exocrine pancreatic deficiency was significantly less (P less than 0.001) than in controls. With one exception no overlap of data was noted. In the group with exocrine pancreatic deficiency, a significant relationship was shown between the PFT and the Lundh test. Reproducibility in duplicate test was excellent. The present data justify further investigations of this procedure as a possible new oral test of exocrine pancreatic function.