Objective To investigate the cause, prevention and treatment of biliary fistula after biliary tract operation.Methods Biliary fistula developed postoperatively in 27 out of 3*!786 patients undergoing bile duct surgery from 1991 to 2000. Results Injury of liver bed cholangiole or tiny accessory hepatict duct occured in 8 cases, 1 developed after incision and exploration of CBD in biliary duct cancer, stump leakage of cystic duct in 7, early T tube inadvertent sliding off or after T tube removement in 10. 21 patients underwent conservative therapy (78%), 6 reoperation (22%). Fistula was cured in 26 cases, the remaining one who suffering from late staged bile duct cancer died. Conclusions Biliary fistula often occurs after cholecystectomy, and after the removal of a T tube. Conservative therapy is often successful unless there is a frank peritonitis, biliary tract obstruction, or improper peritoneal drainage.