A prospective randomized study at a single renal transplant center between 1980 and 1982 compared the influence of leukocyte-depleted versus packed red cell pretransplantation blood transfusions on patient sensitization to leukocyte (HLA) antigens, likelihood of receiving a graft, and eventual transplantation results. All consenting potential cadaver renal transplant recipients (n = 107) were randomly assigned to receive transfusions at 6-week intervals with either packed red cells (Group 1) or leukocyte-poor red cells (Group 2) until they were transplanted. Actuarial graft and patient survival were identical for graft recipients in both groups. Although the likelihood of receiving a graft was associated with the level of pretransplant sensitization to leukocyte (HLA) antigens (p less than 0.02) as measured by the percent of panel reactive antibody (PRA), it was not associated with the type of blood used. The highest mean peak reactive PRA level for all patients showed a low but significant increase (29 +/- 4 versus 43 +/- 5%; p less than 0.0005) following entry into the transfusion protocol, but the rate of increase was the same for patients in both treatment groups. The likelihood of receiving a transplant was primarily associated with a history of prior graft rejection (p less than 0.05), and patients with prior graft loss had the greatest increase in sensitization following entry into the transfusion protocol. These findings indicate that using leukocyte-poor red cells for pretransplant transfusions provided no added benefit when compared with packed red cells in terms of patient sensitization, the likelihood of receiving a transplant, or eventual graft survival.