Data from 7436 cases of first-cadaver transplants between 1981 and 1986 from 50 transplant follow-up centers within Eurotransplant, were analyzed with respect to the effect of HLA-DR matching on graft prognosis within the first year posttransplant. The use of cyclosporine was allowed for as well as the variation in graft survival rate between transplant follow-up centers. After adjustment for these variables, HLA-DR matching was still very significant. The effect of CsA on graft survival varied between centers--i.e., interaction was observed--but the effect of HLA-DR mismatching did not vary significantly between centers. Over all the centers there was a 1.4-fold increase in relative risk for each increase in HLA-DR mismatch, corresponding to predicted one-year graft survivals of 86.5%, 81.9%, and 75.4% for 0, 1, and 2 HLA-DR mismatches respectively, in patients receiving CsA, and 72.5%, 64.2%, and 53.6% in patients not receiving CsA.