One-year graft survival of 54 first cadaveric kidney transplants that received immunosuppressive treatment with CsA was analyzed with respect to the number of random pretransplant blood transfusions and the HLA class 1 and class 2 matching. Overall graft survival at 1 year was 80.7%. Patients with 3 to 20 pretransplant transfusions had a survival of 93.7% compared with 66.7% in those with less than three or more than 20 transfusions. All kidneys transplanted with two or less HLA-A + B mismatches survived at 1 year. With three mismatched antigens survival was of 88.9%. This value was reduced to 66.7% for four incompatibilities. A similar situation was found for HLA-DR matching since all kidneys with full compatibility survived at 1 year compared with 90.9% and 66.7% for one and two mismatches, respectively. HLA-B and HLA-DR exhibited an additive effect since again all grafts with two or less mismatches survived, whereas in the group with three different antigens this figure was 90% and only 1 of the three kidneys with completely different antigens survived.