Evaluate the safety and efficacy of early corticosteroid withdrawal and simultaneous calcineurin inhibitor withdrawal in recipients of primary renal allografts maintained long-term on MMF and sirolimus.

Inclusion Criteria:

• Male and female patients between 18 and 75 years of age.
• Patients who are 90 to 240 days after having received a primary living or cadaver renal allograft.
• Patients maintained on a regimen of cyclosporine or tacrolimus and MMF since transplantation.
• Capable of providing written informed consent.
• No known contraindications to treatment with sirolimus.

Exclusion Criteria:

• Pregnant or lactating.
• Acute rejection within 90 days prior to study randomization.
• More than one biopsy proven acute rejection episode prior to study randomization.
• Previously received or are receiving an organ transplant other than kidney.
• Receiving sirolimus prior to entry.
• Severe diarrhea or other gastrointestinal disorders that may interfere with their ability to absorb oral medication.
• Evidence of active systemic infection requiring antibiotics, or HIV, HCV, HBV infection.
• History of malignancy in the past 5 years.
• Require dialysis at the time of study entry.