A 6-month, open-label, multicenter prospective pilot study was conducted to evaluate the effects of sirolimus (SRL) versus cyclosporine (CsA) in recipients of kidneys from expanded criteria donors. All patients also received antithymocyte globulins induction, mycophenolate mofetil, and steroids. Sixty-nine patients (33 SRL, 36 CsA) were randomized. More patient were withdrawn in the SRL group (16 vs. 6, P<0.01), because of delayed graft function and surgical complications. Delayed graft function tended to be more frequent with SRL than with CsA (45.4% vs. 30.6%, P=0.22). Graft survival was numerically lower in the SRL group (87.5% vs. 97%, P=0.19). At 6 months, there were no significant differences in biopsy-proven acute rejection or calculated creatinine clearance (SRL 12.1% vs. CsA 8.3%; P=0.7 and 44.7+/-16.6 vs. 41.9+/-15.2 mL/min; P=0.54 respectively). These results do not support the use of SRL immediately after transplantation in expanded criteria donor recipients.