Although simple cold storage and hypothermic pulsatile perfusion are each accepted methods of cadaver kidney preservation the efficacy of combining these techniques for extended renal preservation is unclear. In 18 patients cadaver allografts were used that had been preserved with combined simple cold storage (range 6 to 20 hours) and hypothermic pulsatile perfusion (range 9 to 38 hours). The total interval of preservation for these kidneys ranged from 25 to 48 hours. Excellent post-transplant graft function was achieved in all cases, with a mean serum creatinine nadir of 1.4 mg./dl. In 14 patients (78 per cent) grafts continued to function at intervals of 3 to 38 months after transplantation. Of the remaining 4 patients 3 lost the grafts to rejection, while 1 died 7 months after transplantation with a well functioning graft. These data suggest that the combination of simple cold storage and hypothermic pulsatile perfusion provides a safe and effective method for extended renal preservation.