By analyzing 26,414 patients [12,589 with hepatitis C virus (HCV)] in the Scientific Registry of Transplant Recipients database, we sought to determine comparative risk factors (including primary immunosuppression) predictive of death and graft loss among patients with HCV and patients without HCV. Immunosuppression was examined at the baseline and as a time-dependent variable, and the results were stratified by the transplant center and were adjusted for variables well known to affect patient and graft survival. A multivariate analysis of patient mortality demonstrated that recipient age, donor age, hepatocellular carcinoma, diabetes, and creatinine were significantly associated with increased 3-year mortality for both groups. Tacrolimus-based immunosuppression was associated with superior survival in both groups. In contrast, the use of sirolimus was strongly associated with increased mortality in the HCV group, and cyclosporine was associated with increased mortality in the non-HCV group. Adjusting for known and unknown factors predictive of posttransplant outcomes, a propensity analysis confirmed the association of sirolimus use with an increased risk of death in HCV patients as well as the association of tacrolimus use with a decreased risk of death in all patients. In conclusion, this study suggests a novel association between sirolimus use and an increased risk of death and graft loss after liver transplantation in HCV patients that is not seen in patients without HCV. This study confirms the association of tacrolimus with superior outcomes. Sirolimus should be used sparingly in recipients with HCV infections. Liver Transpl, 2012. © 2012 AASLD.