This pilot trial was designed to assess the safety and efficacy of SRL in liver transplant recipients with renal dysfunction. Forty patients with renal dysfunction (24-hr CrCl 40-80 mL/min) were randomized to be withdrawn from the calcineurin inhibitor (CNI) and receive sirolimus (SRL) or to continue CNI (control arm). Improvement in 24-hour CrCl was seen in the SRL arm at 3 months (75 mL/min SRL vs. 56 mL/min control, P=0.012), whereas at 12 months there was a trend toward improvement in the SRL arm (72 mL/min SRL vs. 58 mL/min control, P=0.09). Two patients, one in each arm, developed steroid-sensitive rejection. Side effects of SRL were limited and included hyperlipidemia requiring treatment (15%), pruritus (5%), and mouth sores (25%). In this trial, SRL-based immunosuppression was a safe alternative to CNI. Although early improvements were observed, withdrawing CNI and replacing it with SRL did not result in a statistically significant improvement in renal function at 12 months of follow-up.