At UCSF, we have used sirolimus in several immunosuppression regimens and protocols, and this article will summarize our experience in four areas. The purpose of the first study was to assess the efficacy of a sirolimus-based, calcineurin inhibitor-free regimen for the first 3 months after transplantation. Patients were treated with a calcineurin inhibitor-free regimen that consisted of daclizumab, sirolimus, mycophenolate mofetil (MMF), and conventional corticosteroids. Of nine patients, one (case #7) had an acute rejection episode (type IA) at 2 months after transplantation, which was fully reversed with corticosteroids. The second study was a prospective trial of calcineurin inhibitor-free regimen in patients with severe delayed graft function (DGF) (requiring dialysis). The immunosuppression regimen consisted of daclizumab, sirolimus, MMF, and corticosteroids. This immunosuppressive regimen was effective in patients with DGF; however, it was effective only in non-African American (non-AA) patients (AA had a significantly higher acute rejection rate at 1 year than non-AA, 63% vs 23%, P =.025). In some patients sirolimus was associated with a prolonged recovery from DGF. The addition of sirolimus to immunosuppressive agents provide the opportunity for safe steroid withdrawal (at day 5). We participated in a sirolimus-based, multicenter open-label trial of very early corticosteroid withdrawal. Primary renal transplant patients were enrolled in an immunosuppression regimen that consisted of basiliximab, sirolimus (target levels 8 to 15 ng/mL, 0 to 5 months, and 6 to 12 ng/mL, 6 to 12 months) and tacrolimus in a dose of 0.05 mg/kg BID (target levels 6 to 9 ng/mL). Two of 14 enrolled patients had an episode of acute rejection before steroids were withdrawn. No acute rejection episodes have occurred after steroids were withdrawn (6-month follow-up). The regimen of sirolimus and tacrolimus was well tolerated. Wound complications were not noted. Another important use of sirolimus has been its incorporation in the immunosuppressive regimens in kidney-pancreas transplantation. Our current protocol consists of thymoglobulin induction, combined with MMF, sirolimus, and low-dose tacrolimus, for maintenance therapy. Steroids are only utilized during the first 5 to 6 days following the transplant. This steroid-free maintenance regimen has been used in the last 30 enteric-drained, simultaneous pancreas-kidney transplants. Using this immunosuppressive approach, rejection rates are less than 10% for either the kidney or the pancreas.