BACKGROUND The objective of this study was to clarify the relationship between preoperative exocrine pancreatic function and pancreatic anastomotic leakage after pancreatectomy. METHODS Fifty-five patients who underwent proximal pancreatectomy with pancreaticojejunostomy were reviewed with regard to preoperative exocrine pancreatic function, size of the main pancreatic duct, postoperative pancreatic juice output, and pancreaticojejunostomy leakage. RESULTS There were 32 patients with a normal value at the preoperative N-benzoyl-L-tyrosyl-p-aminobenzoic acid (BT-PABA) excretion test (> 70%) and 23 with a low BT-PABA value (< or = 70%). The greatest diameter of the main pancreatic duct in the group with normal BT-PABA results was significantly smaller than that in the group with low BT-PABA results (4.6 +/- 2.7 mm vs 7.1 +/- 4.2 mm; P < .05). The output of pancreatic juice during a 10-day period (from postoperative days 5 through 14) in the group with normal BT-PABA results was significantly higher than that in the group with low BT-PABA results (1738 +/- 898 mL vs 1072 +/- 1174 mL; P < .05). Pancreatic leakage occurred in 8 (25%) of the 32 patients in the group with normal BT-PABA results and in none of the 23 patients in the group with low BT-PABA results (P < .01). CONCLUSIONS Patients with normal exocrine pancreatic function produce a larger amount of pancreatic juice than those with low exocrine pancreatic function and have a potential risk of anastomotic leakage after pancreatectomy.