Acute humoral rejection should be considered in patients with renal allograft dysfunction. We review the diagnoses, treatments, and outcomes of 8 patients who had acute humoral rejection after a renal transplant. Acute humoral rejection was diagnosed in 8 patients (3 women, 5 men; 16.7 years); 32 had undergone a renal transplant at our center at mean of 19.6 months (range: 10 days to 74 months) after the renal transplant. Acute humoral rejection was diagnosed via allograft dysfunction and allograft biopsy. Allograft biopsy showed a strong, diffusely distributed endothelial staining pattern of CD4 cells in the peritubular capillaries. The results of pretransplant lymphocyte subset analyses and the results of panel reactive antibody tests were normal in all patients. All patients were treated with plasma exchange. Acute humoral rejection occurred in the early postoperative period (<3 months) in 3 patients and in the late postoperative period (>3 months) in 5 patients. Before treatment, the mean serum creatinine level in the 0.6 mg/dL (range, 1.4-3.4 mg/dL) and after treatment, the meanpatients was 2.4 0.6 mg/dL (range, 0.9-2.9 mg/dL). All patients’ whose serum creatinine level was less than 1.9 were treated successfully except 1. In that patient, a graft nephrectomy was done 17 days after the renal transplant owing to total vascular occlusion of the graft. One patient returned to hemodialysis 3 months after treatment, and a retransplant was done 2 months later. At the time of this writing, the remaining 6.36 patients are alive with good graft functioning at a mean follow-up of 14.1 months (range, 7-25 months). In conclusion, widespread CD4 deposition in the peritubular capillaries, as demonstrated by renal allograft biopsy, is an important characteristic for diagnosing acute humoral rejection. In the patients studied here, several plasma exchange treatments were effective in resolving acute humoral rejection.