The purpose of this study was to define risk factors for acute rejection with early corticosteroid withdrawal (CSWD; within 7 days posttransplant) in renal transplantation. Data from prospective, IRB-approved early CSWD trials were analyzed. Overall acute rejection rate in 308 patients was 17.1%. Acute rejection rates and observed risks (OR) in patients with individual risk factors were: repeat transplants 38.6%; current PRA >25%; 29.4%; African Americans 23.5%; delayed graft function (DGF) 26.1%; HLA DR mismatches >0 17.9%; female gender 19.7%; Thymoglobulin induction 15.3%; type 1 diabetes 30.8%; type 2 diabetes 11.1%; deceased donor recipients 21%; and living donor recipients 14%. Logistic regression analysis provided the following risks (OR) for acute rejection: repeat transplant 2.51; current PRA > 25% 1.53; African Americans 1.47; DGF 1.58; HLA DR mismatches > 0 1.61; female gender 1.43; Thymoglobulin induction 0.61; type 1 diabetes 2.23, type 2 diabetes 0.5, deceased donor recipients 1.11, and living donor recipients 0.9. Risk factors for acute rejection under early corticosteroid withdrawal are similar to those previously defined under chronic corticosteroid therapy. These observations provide implications for future CSWD trials including: use of T cell depleting antibody induction therapy (thymoglobulin) to reduce acute rejection risk, 2) enrollment stratification for high risk groups, and 3) modified immunosuppression for high risk groups.