The effect on cadaver-kidney transplant survival-rates of a gamma-globulin concentrate, prepared from clotted blood centrifugally expressed from placental tissue recovered from postpartum women, was evaluated in a prospective controlled trial in 195 patients who were also given a standard immunosuppressive regimen. Allograft-survival rates were analysed according to whether or not the recipient had lymphocytotoxic antibodies before transplantation (responders) and whether the graft was a first or second transplant. The graft-survival rate was improved in responder-type recipients of first transplants who had received the gamma-globulin concentrate as adjunctive therapy (control group 28.8+/-10.1% vs. gamma-globulin 55.5 + 9.7% at 2 years, p less than 0.05). The survival-rate of grafts in non-responders was not affected by administration of gamma-globulin and data on its use in recipients of a second graft were insufficient for analysis. These results suggest that the gamma-globulin concentrate was suppressing immunological responses associated with humoral-type rejection.