We reviewed 115 cases of acute rejection following renal transplantation. All cases were diagnosed after graft biopsy, and showed histopathological evidence of acute rejection. They were treated with administration of OKT3, 15-deoxyspergualin (DSG), anti-lymphocyte globulin (ALG) or methylprednisolone (MP). All rejections were histopathologically classified according to the Banff working classification. The clinical effects of each drug were evaluated both at 1 month and 1 year following the therapy for rejection, by measurement of serum creatinine level. The effective rate both at 1 month and 1 year was related with the Banff working classification ( p < 0.0001). At 1 month after treatment, there were no significant differences between the OKT3, DSG or ALG group and MP group in cases of borderline change and AR grade I. In cases of grade II and grade III, a significant difference was observed between the OKT3 or ALG group and MP group (p < 0.05). The DSG group showed a slightly better outcome than the MP group, although the difference was not significant. In conclusion, the Banff schema is shown to be valid for classification of acute renal allograft rejection, and it is necessary to determine the treatment for acute rejection according to histopathological classification.