The major problem in clinical transplantation is the imbalance between the need for cadaveric organs and the available numbers of donors. If pediatric kidneys were transplanted into adult recipients when no pediatric recipient was available, the potential number of renal donors would be increased by 15 to 20%. Some centers are reluctant to use pediatric kidneys for adult recipients because of recent reports indicating poorer patient and allograft survival, increased delayed graft function, increased post-transplant hypertension and increased technical complication. (There also has been concern that the nephrotoxic effect of cyclosporine A would retard the organ growth that is necessary to provide normal renal function in adults.) A retrospective analysis was performed on 18 adult recipients who received kidneys from cadaver donors 14 months to 12 years old (group 1). These patients were compared to 106 adult recipients who received kidneys from donors greater than 12 years old (group 2). Actuarial patient survival at 1 year was 85% for group 1 and 95.8% for group 2 (p equals 0.13), while 1-year actuarial allograft survival was 83.1% for group 1 and 81.1% for group 2 (p equals 0.87). There was no significant difference between groups 1 and 2 in the frequency of delayed graft function, serum creatinine at 1, 3 and 6 months after transplantation, incidence of post-transplant hypertension or frequency of surgical complications. It is of interest that the pediatric kidneys had significant growth during the initial post-transplant month. Sonographic examination at postoperative days 1 and 30 demonstrated a mean increase in size from 80.7 to 143.5 cm. (p less than 0.001). In this series pediatric kidneys were safe and effective donor organs in adult recipients, and increased the available number of organs by 15%.