Sixteen symptom-free siblings of children with vesicoureteral reflux were found to have the condition and underwent renal scintigraphy with technetium 99m dimercaptosuccinic acid. Of these 16 children, 6 had scintigraphic evidence of renal damage. Screening for vesicoureteral reflux in siblings of children known to have the condition should therefore be carried out early in life; when reflux is present, an immediate assessment of the renal parenchyma should be made.