Treatment options are limited for orthotopic liver transplant (OLT) recipients suffering from chronic rejection (CR). We performed a retrospective review of OLT recipients diagnosed with CR and treated with sirolimus. The medical records of all OLT recipients treated with sirolimus between October, 1998 and October, 2000 were retrospectively reviewed. The diagnosis of CR was made by both clinical and histologic criteria: bile duct to hepatic artery ratio less than 0.7, histologic activity index, hepatic arterial wall thickening, and chronic elevation of liver chemistries. Two groups were defined in regard to sirolimus response: sirolimus responders (SR) and sirolimus nonresponders (SNR). Response to treatment was granted only when patients were found to have resolution of abnormal liver transaminases and an improvement in hepatic artery to bile duct ratio. Serum collections for liver chemistries were collected on days 1, 30, 60, and 90. Liver biopsies were reviewed in blinded fashion from day 1 and at least 180 days on therapy by double-blinded pathologists. Sirolimus-related complications were recorded and include drug toxicity, anemia with and without treatment, hospitalizations, infections, immunosuppression complications, lipid profile disorders, edema, muscle aches, and gastrointestinal complaints. Twenty-one patients were diagnosed with CR. The SR group included 13 of 21, and 8 of 21 were in the SNR group. Anemia was diagnosed in 12 of 21 patients: SR, 7 of 13; SNR, 5 of 8; with 5 patients requiring red blood cell transfusions (2 SR, 3 SNR). Recombinant erythropoietin was started in 5 of 21 patients. Sirolimus serum levels were found to be greater than 20 ng/dL in 12 patients. Sirolimus was discontinued in 9 patients,