In the present study of 31 kidneys transplanted from donors ranging in age from one to one-half to nine years, the ability of kidneys from donors in the pediatric age group to provide adequate renal function in adults is evaluated. Kidney function was reviewed six months, one year, three years and five years after transplantation. Forty per cent of the transplanted kidneys from this age group had excellent function at six months. Of the kidneys at risk for five years, 30 per cent were still functioning. Kidneys from donors three years of age and younger developed a creatinine clearance rate of 20 milliliters per minute in 12 days or less. Maximum creatinine clearance rates for kidneys from donors of the pediatric age group equaled those of adult donors. In addition, recipients of pediatric kidneys after one year tended to maintain a lower creatinine level than did their counterparts receiving adult kidneys. Thus, kidneys from donors as young as 18 months of age can be transplanted individually without special difficulties and can be expected to provide excellent renal function for adult recipients.