Background: Despite the potentially severe impact of bile leakage on patients' perioperative and long-term outcome, a commonly used definition of this complication after hepatobiliary and pancreatic operations has not yet been established. The aim of the present article is to propose a uniform definition and severity grading of bile leakage after hepatobiliary and pancreatic operative therapy. Methods: An international study group of hepatobiliary and pancreatic surgeons was convened. A consensus definition of bile leakage after hepatobiliary and pancreatic operative therapy was developed based on the postoperative course of bilirubin concentrations in patients' serum and drain fluid. Results: After evaluation of the postoperative course of bilirubin levels in the drain fluid of patients who underwent hepatobiliary and pancreatic operations, bile leakage was defined as bilirubin concentration in the drain fluid at least 3 times the serum bilirubin concentration on or after postoperative day 3 or as the need for radiologic or operative intervention resulting from biliary collections or bile peritonitis. Using this criterion severity of bile leakage was classified according to its impact on patients' clinical management. Grade A bile leakage causes no change in patients' clinical management. A Grade B bile leakage requires active therapeutic intervention but is manageable without relaparotomy, whereas in Grade C, bile leakage relaparotomy is required. Conclusion: We propose a simple definition and severity grading of bile leakage after hepatobiliary and pancreatic operative therapy. The application of the present proposal will enable a standardized comparison of the results of different clinical trials and may facilitate an objective evaluation of diagnostic and therapeutic modalities in the field of hepatobiliary and pancreatic operative therapy.