Familial aggregates of incomplete Müllerian fusion have been reported, but the role of genetic factors has not been elucidated. In the last several years, we have fortuitously encountered three families in which several members were affected with Müllerian fusion anomalies. In two families, several members had incomplete Müllerian fusion as traditionally described. In the third family, several members had the hand-foot-genital syndrome, a rare autosomal dominant disorder characterized not only by Müllerian fusion defects but also by skeletal (hand and foot) malformations. The etiologic heterogeneity of Müllerian fusion defects is considered.