This study focuses on the beneficial effect of HLA matching on long-term graft survival rates in CsA-treated living primary kidney transplants at Catholic Medical Center, 1984 to 1993. 1. An impressive 26% difference in kidney graft survival was observed at 5 years between recipients who received 0 and 2 HLA-DR mismatches (79% vs 53%). 2. Five-year kidney graft survival rates in the 0, 1, 2, and 3-HLA-B+DR mismatches were 87%, 76%, 77%, and 74%, respectively, which was significantly different from 54% survival rates in the 4-HLA-B+DR mismatch group. 3. The 5-year kidney graft survivals in the 0, 1, 2, HLA-DR-mismatched living-nonrelated donor group were 84%, 76%, and 39%, respectively, which were significant differences. 4. The 5-year kidney graft survivals in the 0, 1, 2, HLA-DR-mismatched living-related donor group were 75%, 79%, and 72%, respectively, which were not significant. 5. The effect of HLA-A, B, A+B, A+DR, and A+B+DR mismatches showed little difference among the groups with different mismatch numbers. In conclusion, better matching for the HLA-DR, B+DR antigens significantly improved kidney graft survivals in our CsA-treated primary living-donor transplant recipients.