Two hundred twenty-eight patients from a total of 466 (49%) receiving renal allografts under cyclosporine/prednisone (CsA/Pred) immunosuppression experienced at least one episode of posttransplant hepatotoxicity. All patients were documented to have normal serum bilirubin, serum glutamic oxaloacetic transaminase (SGOT), serum glutamic pyruvate transaminase (SGPT), lactic acid dehydrogenase (LDH), and alkaline phosphatase (AP), as well as negative results of biliary ultrasound and upper gastrointestinal contrast examinations prior to transplantation. Hepatotoxic episodes usually were self-limited (82%), and generally occurred during the very early posttransplant period (76%). Liver function abnormalities included hyperbilirubinemia (48% of patients), elevated SGOT (47%), SGPT (73%), LDH (84%), and AP (59%). The CsA serum trough radioimmunoassay (RIA) was relatively high among hepatotoxic patients with a mean value of 225 +/- 17 ng/ml. Pharmacokinetic parameters, including bioavailability and drug clearance, were significantly altered among this group of patients. The management strategy of CsA dose reduction was effective; however, 11 patients (2.4%) developed biliary calculous disease posttransplant while under CsA/Pred immunosuppression. Seven patients had cholelithiasis, and two patients underwent choledochoduodenostomy because of primary choledocholithiasis. The results contrast with 279 renal transplant recipients from an overlapping nonrandomized group treated with azathioprine (Aza)/Pred in whom cholelithiasis was not identified. Pancreatic abnormalities were relatively common, but clinical pancreatic disease occurred in only six patients. There were two episodes of acute pancreatitis, three patients developed pancreatic abscess, and one patient developed a pancreatic pseudocyst. The apparent proclivity of CsA-treated patients to develop biliary calculous disease, and the occurrence of serious pancreatic complications in a small percentage of patients did not affect the majority of CsA-treated patients. They may, however, represent important problems associated with the use of this immunosuppressive agent.