Patients awaiting a renal transplant were given 1 HLA-DR antigen-matched blood in order to compare the sensitization and graft outcome of these patients with those of control patients, who had been given random blood before transplantation. No differences in sensitization, measured by the formation of HLA antibodies, or in graft survival were found between the 2 groups. However, the incidence of rejection episodes was significantly reduced in the patients who received blood matched for 1 HLA-DR antigen compared with the patients who received random blood.