Liver biopsy is an important diagnostic tool in the management of patients following orthotopic liver transplant. We evaluated complications following percutaneous liver biopsy in a group of liver transplant patients who had Roux-en-Y choledochojejunostomies fashioned as part of their biliary reconstruction during liver transplantation. Complications were divided into two major groups: septic complications (including fever, symptomatic bacteremia, cholangitis, infected hematoma and hypotension related to sepsis) and bleeding (defined as hypotension requiring volume expansion greater than 500 cm3 or blood transfusion, hemothorax, intrahepatic or peritoneal hemorrhage and hemobilia occurring within 1 wk of liver biopsy). One hundred ninety-two biopsies were performed in 46 patients with choledochojejunostomies, and 118 biopsies were carried out in an age- and sex-matched control group of patients with choledochocholedochostomy biliary anastomosis. There were no septic complications in the choledochojejunostomy patients and one (0.32%) septic complication in the choledochocholedochostomy patients (NS). Eight bleeding complications occurred (2.6%) in eight patients (8.3%). Five (2.6%) occurred in five (10.8%) of the choledochojejunostomy patients, vs. three (2.5%) in three (6.5%) choledochocholedochostomy patients (NS). None of the bleeding complications required surgical intervention or was fatal. We conclude that liver biopsy in posttransplant patients with Roux-en-Y choledochojejunostomies is a safe procedure and that the incidences of complications were similar in our two groups. The negligible incidence of septic complications in the choledochojejunostomy patients does not appear to warrant the administration of prophylactic antibiotics, as has been previously suggested. (HEPATOLOGY 1994;20:651–653).