1. The effect of donor-specific blood transfusions (DST) on renal graft survival of HLA one haplotype-mismatched living-related transplant patients was studied, and 1,292 transplant patients reported in the Japanese Renal Transplant Registry were analyzed. In the CsA groups, the graft survival rate at 4 years of the DST, DST plus unspecified blood transfusion (UTF), UTF, and no blood transfusion (TF = 0) groups, were 93.5%, 91.6%, 76.2%, and 62.7%, respectively, whereas, in the conventional groups, the graft survival rate at 4 years of the DST, DST plus UTF, UTF, and TF = 0 groups were 73.3%, 87.2%, 73.2%, and 69.0%, respectively. 2. The superior DST effect was prominent in the transplants on CsA, but not in those on conventional immunosuppression. The DST patients receiving UTF, however, showed a superior DST effect. 3. DST patients treated with conventional immunosuppression and the CsA patients receiving UTF showed an equal graft survival rate. 4. Since the CsA therapy was able to achieve a higher graft survival rate in a high MLR combination (S.I. greater than 10), it is likely that the DST patients treated with CsA showed an excellent graft survival rate. 5. The transplant patients without blood transfusion in the CsA and conventional groups achieved a moderate graft survival rate.