A simple breath test was developed for assessment of exocrine pancreatic function employing 13C-dipeptide [ie, benzoyl-L-tyrosyl-[1-(13)C]alanine (Bz-Tyr-Ala)], and this test was examined to determine whether it can be used to diagnose exocrine pancreatic insufficiency in patients with chronic pancreatitis. The subjects, 24 patients with chronic pancreatitis and 16 healthy adult controls, underwent the Bz-Tyr-Ala breath test, in which breath samples were collected every 10 min up to 90 min after oral administration of an aqueous solution of 5-mg/kg Bz-Tyr-Ala (7 mM). They also underwent a breath test with [1-(13)C]alanine equimolar to that contained in Bz-Tyr-Ala and the N-benzoyl-L-tyrosyl-p-aminobenzoic acid (BT-PABA) test. Delta13CO2 values at 10-60 min for the Bz-Tyr-Ala breath test were significantly lower in chronic pancreatitis patients than in normal controls. However, the [1-(13)C]alanine breath test results did not differ between patients and normal controls. The correlation coefficient between the Bz-Tyr-Ala breath test Delta13CO2 value at 20 min, and the results of the BT-PABA test were r=0.726 (r2=0.527, P<0.0001). The results suggest that this newly developed Bz-Tyr-Ala breath test can quickly and noninvasively diagnose the exocrine pancreatic dysfunction.