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New immunosuppressive drugs such as anti-interleukin-2 receptor antibodies (aIL2R) and mycophenolate mofetil (MMF) have reduced the incidence of acute rejection after renal transplantation. Whether matching donor and recipient human leukocyte antigen (HLA) antigens is still relevant in patients receiving modern immunosuppression has been questioned.We retrospectively analyzed the incidence and risk factors of acute rejection during the first posttransplant year and the impact of acute rejection on long-term graft survival in a cohort of 208 renal transplant patients treated with aIL2R (basiliximab, n=166; daclizumab, n=42), calcineurin inhibitors (tacrolimus, n=180; cyclosporin, n=28), mycophenolate mofetil, and steroids. Graft and patient survival were calculated by the Kaplan-Meier method. Risk factors for acute rejection were analyzed by logistic regression modeling.Twenty-seven patients were treated for acute rejection (26 biopsy-proven) during the first posttransplant year. The Kaplan-Meier estimate of first-year acute rejection was 13.2%. The number of HLA mismatches (odds ratio [OR] 1.65 per HLA mismatch) and long periods of dialysis before transplantation (OR 3.1 for more than 4 years of dialysis) were the only independent risk factors for first-year acute rejection. First-year acute rejection was associated with a significant reduction in overall and death-censored graft survival at 5 years after transplantation.Although infrequent in patients receiving modern immunosuppressive drugs, acute rejection remains an important risk factor for graft loss after renal transplantation. Our results suggest that better HLA matching and shorter periods of dialysis before transplantation could reduce acute rejection rates and further improve outcomes under current immunosuppressive regimens.