Analysis for over 1000 kidney retransplants revealed an important effect of 1st graft duration and presensitization on graft outcome. Second cadaver donor grafts into patients without preformed cytotoxic antibodies and a 1st graft duration of more than 12 mo. survived at a high 1-yr rate of 71 .+-. 6%, in contrast to 29 .+-. 6% in those whole 1st graft had failed in 1-3 mo. (P < 0.0001). Third or 4th transplants into patients with preformed cytotoxins survived at the poor rate of 17 .+-. 6% at 1 yr. A repeat of all HL-A mismatches from the 1st graft decreased 2nd graft survival.