OBJECTIVE To examine the feasibility and significance of 13C-Hiolein breath test in evaluating chronic pancreatitis-related exocrine insufficiency and efficacy of enzyme treatment. METHODS The 13C-Hiolein breath test was used in 8 healthy volunteers (group 1), 8 chronic pancreatitis (CP) patients without steatorrhea (group 2), and 8 CP patients with steatorrhea (group 3). To evaluate the function of pancreatic exocrine, 13CO2 was determined following 13C-Hiolein diet. The 13C-Hiolein test was repeated in group 3 after enzyme supplement therapy. RESULTS Administration of 13C-Hiolein diet resulted in significantly higher cumulative percent dose of 13C recovery per 6 h (cPDR/6 h) and maximal PDR (PDR(peak)) in the healthy controls (group 1) than the CP patients with steatorrhea (group 3) (11.22%+/-1.22% and 6.11%+/-0.59% vs 2.87%+/-0.73% and 1.53%+/-0.36%, respectively, both P<0.01). In the CP patients with steatorrhea (group 3), a repeated test after enzyme supplementation therapy showed a significant elevation of both cPDR/6 h and PDR(peak) (9.03%+/-0.84% and 2.33%+/-0.47%, both P<0.01 compared with those before enzyme treatment), but cPDR/6 h remained significantly lower than that in the healthy volunteers (group 1, P<0.05). Both cPDR and PDR(peak) in the CP patients without steatorrhea (group 2) were similar to those in the healthy controls (group 1, both P>0.05). CONCLUSION The results of 13C-Hiolein breath test well reflect fat metabolism status in CP patients, and the test can be used to monitor the efficacy of pancreatic enzymes therapy.