Abstract A sensitive crossmatch that employs kidney cells and the immune adherence or mixed agglutination techniques has been devised and applied prospectively together with a lymphocytotoxicity crossmatch to the selection of cadaver kidneys for retransplantation in 11 consecutive patients. All of these recipients had rejected one or more previous transplants—in four cases by hyperacute rejection—and seven had cytotoxic antibodies (8 to 56 per cent). The functional survival rate of these cadaver kidney retransplants was 82 percent at nine months and patient survival was 100 percent. Current serum creatinines range from 0.8 to 1.8 mg. per 100 ml. These results contrast with 30 previous cadaver kidney retransplants for which the nine-month graft survival was 41 percent and patient survival 70 percent. The discontinuance of azathioprine before removal of a rejected transplant adversely affected the survival of a subsequent transplant and contributed to the poor results seen in the earlier group. Three retransplants from living related donors have excellent function at six months to nine years. The prospective kidney cell crossmatch is a promising technique for the improvement of cadaver kidney survival in highly immunized recipients who have rejected previous transplants. Azqthioprine or other immunosuppressive therapy should be continued until a rejected transplant is removed in order to avoid sensitization to a subsequent transplant.