Renal agenesis/adysplasia is the leading etiology of end stage renal disease in children. The etiology for renal agenesis/adysplasia has not been identified. The purpose of the present study was to determine if renal agenesis/adysplasia occur in a familial pattern. Twenty seven cases of bilateral renal agenesis/adysplasia were identified by review of autopsy records, and four were excluded. A male excess of 2.8:1 was noted with a mean gestation of 35 weeks. Prenatal and family histories were obtained on 11/23 families. Potential embryologic stressors were identified in 8/11 pregnancies. Thirty-four 1st and 2nd degree relatives from five families participated in a renal ultrasound exam. An increased prevalence of congenital renal anomalies was identified in the relatives of index patients with bilateral renal agenesis/adysplasia (14.7%) compared to controls (2.2%), with a recurrence risk of 6.2 for 1st degree relatives. The most frequently identified renal anomalies in the family members were solitary kidneys and duplicated collecting systems. The increased prevalence of a range of renal anomalies within affected families raises the possibility that isolated renal malformations result from unidentified gene-environment interactions.