We report a prospective, open-label, randomized study to evaluate the safety and efficacy of converting patients with a stable renal function from tacrolimus (Tac)-based regimen to a sirolimus (SRL)-based regimen after kidney transplantation. Fifty-eight low-risk renal allograft recipients who receiving Tac 6 months posttransplant, were randomly assigned to continue Tac (n = 29) or convert to SRL (n = 29). We evaluated the 3-year outcomes including patient and graft survival, graft function, and safety profile. Three-year patient and graft survival in SRL and Tac groups were 93.1% versus 100% (P = 0.32), and 89.7% versus 100% (P = 0.11), respectively. However, the SRL group had a significantly better renal function, from the 2nd year posttransplant until the last follow-up. Four (13.8%) patients in the SRL group and 3 (10.3%) in the Tac group (P = 0.5) developed biopsy-proven acute rejection. Mean urinary protein excretion increased significantly after SRL conversion. Diastolic blood pressure was significantly lower at the end of the study in patients who eliminated Tac (80.4 vs. 75.6 mmHg in Tac and SRL group, respectively) (P = 0.03). Mean hemoglobin concentrations decreased after SRL conversion and remained significantly lower from 12 months to 36 months (P = 0.01). The mean serum cholesterol (540 ± 44 mg/dl) and triglyceride (177 ± 27 mg/dl) increased significantly in the SRL group, compared to Tac group (487 ± 62 mg/dl) (P = 0.03) and (141 ± 26 mg/dl) (P = 0.04). Our experience demonstrates that conversion to SRL from calcineurin inhibitors-based therapy may result in better renal function and blood pressure control in renal transplant recipients without an increased risk of acute rejection. However, these benefits have not resulted in a growing advantage in graft or patient survival.