A prospective study was begun more than 10 years ago to identify the incidence of vesicoureteral reflux in the siblings of patients with reflux. A total of 354 siblings of 275 index patients was screened with a voiding cystourethrogram for the presence of reflux. Of the siblings tested 119 (34%) were found to have reflux, including 75% who were asymptomatic. Reflux was present in a significant percentage of younger siblings. No correlation with index patient reflux grade, sex or established renal damage could be related to the likelihood of sibling reflux. A slightly higher rate of reflux was found in the female siblings of female index patients, which is a variation from the initial study. The incidence of renal damage was significantly reduced in the siblings with reflux compared to the index patients, which was also true in the youngest patients, who are believed to be the most susceptible to reflux-mediated renal damage. Sibling reflux screening can be justified due to a high percentage of siblings found to have reflux without symptoms and a significant decrease in renal damage compared to the index patients. Aggressive screening in young children (less than 5 years old) is still advisable, although this recommendation has been modified for older children. Additional information will be needed before the genetic transmission of reflux can be clarified.