Withdrawal of steroid therapy in renal transplant recipients is associated with a risk of acute allograft rejection. To define clinical risk factors for rejection associated with steroid withdrawal, we analyzed the clinical characteristics of 107 patients with drawn from steroid therapy at various times after transplantation. Both univariate and multivariate analyses suggested that the timing of steroid withdrawal is an important predictor of steroid withdrawal failure. Withdrawal of steroids was successful in only 13 of 32 patients (41%) in whom prednisone was discontinued shortly after transplantation. In contrast, steroid withdrawal has been successful in 59 of 75 patients (79%) in whom prednisone was discontinued at least 6 months after transplantation. Black race and donor-recipient racial mismatch also were significant predictors of rejection associated with steroid withdrawal. In patients undergoing steroid withdrawal at least 6 months posttransplant, serum creatinine concentration also correlated independently with the risk of rejection. Neither age, sex, HLA match, pretransplant PRA, source of the allograft (cadaver vs. living relative), acute tubular necrosis, nor the presence of diabetes was predictive of the outcome of steroid withdrawal.