Siblings of patients with vesicoureteral reflux (VUR) are reported to have an increased incidence of reflux. We present 16 families with 33 affected children out of a total of 493 patients with VUR. Twenty-seven had urinary tract infection and 6 were asymptomatic and were examined because a sibling had VUR. Renal scarring was present in 19 cases; reflux was more marked and more often bilateral in the siblings than in sporadically affected children. In view of our findings we suggest that siblings of patients with VUR be screened early for reflux to prevent renal damage from untreated VUR.