Most renal failure in children results from congenital anomalies of the kidney and urinary tract (CAKUTs). Sanna-Cherchi et al. predict that by 30 years of age, nearly 50% of patients with a solitary kidney would be receiving dialysis. This outcome differs markedly from that of renal-transplant donors, who have no increased risk for renal failure. Because morbidity from CAKUTs may not develop until adulthood, these patients should be closely followed throughout life.