Receiver operating characteristic (ROC) analysis was used to assess the use of the serum chemical markers, gamma-glutamyl transferase (GGT), alkaline phosphatase (AP), and total bilirubin (BR) as tests for biliary complications in patients who had undergone orthotopic liver transplantation. Our study consisted of 105 consecutive adult transplant patients at the University of Chicago from March 1985 to November 1988. Biliary complications were determined by cholangiogram. Maximum serum values for three postoperative time periods (days 0 to 30, days 31 to 90, and > 90 days) were obtained for each patient. ROC analysis showed that GGT was the best single test during the earliest and latest time periods, whereas BR was best during days 31 through 90. We also assessed the time periods, surgical biliary anastomosis, pretransplant diagnosis, and location of biliary lesions compared with the incidence of biliary pathology for the patients. We found that patients with a pretransplant diagnosis of acute parenchymal liver disease were more likely to have biliary complications, and patients with end-to-end anastomosis with T tube were also more likely to have biliary complications. We further conclude that GGT, BR, and AP are all useful in screening for biliary complications and should be used routinely in liver transplant patients.