Pediatric recipients comprised 6% of first cadaver transplants, 9% of cadaver retransplants, and 4% of parent donor transplants reported to the UCLA Transplant Registry between January 1984 and December 1989. 2. Very young pediatric patients (aged 1-5) had consistently poorer 1-year graft survival than older pediatric or adult recipients. Graft survival was 65%, 46%, and 86% at 1 year for first cadaver, cadaver regrafts, and first parent donor transplants, respectively. The comparable ranges for recipients over 5 years old were 73-77%, 65%, and 88%. 3. The poor outcomes for very young pediatric recipients of first cadaver transplants were mitigated by using adult male donor kidneys (75% 1-year survival) and HLA-B,DR matching (75% 1-year graft survival with 0-1 B,DR mismatch). 4. One-year graft survival improved from 66-78% with pretransplant transfusions in 11 to 18-year-old first cadaver transplant recipients (p less than 0.05), whereas transfusions improved 1-year graft survival in adult recipients by only 3%. 5. Cadaver kidneys from donors aged 1-5 yielded the lowest 1-year graft survival rate in first transplants (68%) and in regrafts (46%), whereas those from donors aged 16-18 yielded the best results (81% in first transplants and 66% in regrafts). 6. The poorest graft survival rates for each recipient age group resulted with kidneys from very young donors (aged 1-5). The lowest survival rate (51%) resulted when kidneys from donors aged 1-5 were used for recipients aged 1-5. 7. Prolonged CITs in excess of 30 hours had an extremely adverse effect on kidneys from donors aged 1-5. Kidneys from donors aged 1-5 with less than 18 hours CIT yielded 75% 1-year first transplant survival, whereas only 57% of those with more than 30 hours CIT survived. 8. The overall poorer outcome for very young pediatric recipients was apparently due to the use of age-matched donors for this group. Over 40% of first transplant recipients aged 1-5 received cadaver kidneys from donors aged 1-5.