Between January 1, 1978, and August 31, 1985, 13 infants aged 6 to 11 months received primary renal transplants (12, living related donor; one cadaver) at the University of Minnesota. Twelve infants are alive with functioning grafts (10 primary and two second transplants) after 4 months to 7.5 years. To assess the long-term outcome, we analyzed growth and development in the first nine infants 2 to 7.5 years after receiving their first transplant. Before transplantation, head circumference and height standard deviation scores in six of nine infants were less than -2. Five had seizures; four had delayed mental development, and six delayed motor development. The mean increment in height standard deviation scores for six boys after transplantation was +1.4 (P less than 0.05), and one achieved complete catch-up growth. The mean difference in height standard deviation scores for three infant girls with primary hyperoxaluria was -2.1; nevertheless, two infants with oxalosis are currently alive 2.7 to 3.3 years later. All eight surviving children achieved normal head circumference (mean improvement +2.2 SDS, P less than 0.001), and no child had further seizures. Of seven infants reassessed with the Bayley Scales after transplantation, mental development was normal in all and motor development was normal in five. Our findings suggest that early living related renal transplantation is an important option in the management of end-stage renal disease in infants.