The transfusion effect in first cadaver kidney transplants was re-examined at the UCLA Transplant Registry. One-year graft survival rates were 71% for nontransfused patients, which improved to 75% (P<0.05) with a single transfusion, 77% (P<0.01) with 2 and 78% (P<0.01) with 3 and 4 transfusions. One-year graft survival rates did not improve further with additional transfusions but remained at the same level. Thus, the transfusion effect clearly does exist, and 2 to 4 transfusions are sufficient to obtain the maximum beneficial transfusion effect. Patients with zero HLA-DH mismatched transplants had no blood transfusion effect. Transfusions improved the 1-year graft survival rate by 8% for transplant recipients with 1 DR-mismatched grafts (P<0.01) and by 10% with 2 DR-mismatched grafts (P<0.01). The transfusion effect was greater in Black than White recipients; however, the 77% 1-year graft survival rate for transfused Black recipients of zero DR-mismatched kidneys did not differ from thatof transfused omparably matched Whites. We conclude that transfusion protocols should not be abandoned unless patients receive zero DR-mismatched kidneys. © 1990 by Williams and Wilkins.