Experience with 35 second grafts included in a total number of 310 renal transplants was analyzed to identify factors associated with success. The 2 year life-table renal survival rate of sequential cadaveric grafts is 42 percent compared in 54 percent for primary cadaveric grafts. The 2 year life-table patient survival rate for the same group is 68 percent compared to 72 percent for single cadaveric homotransplants. Twenty-one of 30 patients tested in the interval between grafts developed cytotoxic antibodies to greater than 5 percent of a random panel of cells; 43 percent of these kidneys functioned at least one year; 65 percent functioned for one year or more if the cytotoxicity was 5 percent or less. If the first graft functioned greater than 3 months, the second had a 67 percent chance of functioning for one year; if less than 3 months, the second had a 45 percent one year function rate. Removal of the first transplant at time of second transplantation resulted in an 88 percent one year life-table survival rate of the second kidney in nine patients. Removal prior to second transplantation resulted in a 25 percent one year survival rate in 23 patients. To further evaluate this significant finding, data was obtained through the American College of Surgeons/National Institutes of Health (ACS/NIH) Organ Transplant Registry from five major transplant centers. Thirty-two patients had their first graft removed at time of second transplantation with a 52 percent one year life-table kidney survival rate vs. 29 percent if the first were removed more than 90 days prior to second grafting. Statistical analysis shows this to be significant at the 95 percent confidence level.