Of 304 children who received primary renal transplants at the University of Minnesota between January 1, 1968, and December 31, 1985, 48 (16%) were under the age of 24 months, 60 (20%) were 2-5 years old, and 196 (64%) were 6-17 years old at transplantation. Currently, 254 (84%) are alive at 2 months to 18 years following their first transplants, 77% with functioning grafts (188 first, 45 retransplants) and 7% on dialysis. Overall, patient and graft survival were not significantly different from the primary graft outcome of nondiabetic adults. The actuarial primary graft function rates at 1, 5, and 10 years were 100, 100, and 90% in 16 HLA-identical sibling kidneys; 84, 64, and 52% in 210 mismatched related kidneys; and 72, 54, and 47% in 78 cadaver kidneys (p < 0.002). The 1-year patient survival and primary graft function rates in 44 mismatched related recipients under the age of 24 months were 92 and 88%. The use of deliberate, pretransplant random blood transfusion since 1979 has been associated with a decreased rejection rate. Primary graft function of mismatched related kidneys in children receiving standard immunosuppression has significantly improved from 78% at 1 year in the pretransfusion era to 91% (p < 0.01) in the transfusion era. The overall primary cadaver graft function rate, however, did not improve in the transfusion era. Whether cyclosporine use will improve the cadaver renal allograft function in very young recipients remains to be established. However, with the use of related donors, even very young children can be transplanted safely and with excellent results.