This 2-arm study recruited kidney transplant patients who were receiving standard care of calcineurin inhibitors (CNIs, tacrolimus or cyclosporine), CellCept (1.0-1.5 g twice daily) and corticosteroids. They were either randomized to continue this regimen, or CNI therapy was discontinued and replaced by sirolimus therapy (in combination with CellCept and corticosteroids). The effect of these 2 regimens on efficacy, safety and kidney function was evaluated. The anticipated time on study treatment was 1-2 years, and the target sample size was 100-500 individuals.