The object of the present study was to confirm the HLA-DRB1 matching effect on rejection crisis, its severity, and kidney graft survival based on genotyping. Ninety-four renal allografts were included in this study. DNA typing of HLA-DRBI was performed by the polymerase chain reaction sequence-specific oligonucleotide method. The incidence of acute rejection within 6 months following transplantation, the frequency of OKT3 administration for steroid-resistant rejection, histopathological findings, and graft survival rate were compared between the DRB1-matched (n = 23) and DRB1-mismatched (n = 71) groups. Four acute rejections occurred in the DRB1-matched group (incidence; 17%) and 40 in the DRB1-mismatched group (56%). In the DRB1-matched group, the incidence of acute rejection was significantly less frequent than that of the DRB1-mismatched group (P < 0.005). In the DRB1matched group, only one patient received OKT3 administration (4%), in contrast to 16 of 71 patients in the DRB1-mismatched group (23%). The use of OKT3 was significantly less frequent in the DRB1-matched group (P < 0.05). Histopathological findings from biopsy specimens showed no constant distribution of pathological grades of acute rejection according to DRB1 matching in the present study. The graft survival rate in the two groups did not differ significantly, but the graft survival rate in the DRB1-mismatched group had a tendency to decrease as the grafts survived longer. In conclusion, the results of the present study confirm that HLA-DRB1 matching has marked beneficial effects on kidney transplants through reduction of the acute rejection rate and decrease of the severity of rejection, and suggest that improvement of graft survival will be obtained through kidney allocation to a DRB1-matched recipient.