Familial aggregates of incomplete Mullerian 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 Mullerian fusion anomalies. In two families, several members had incomplete Mullerian 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 Mullerian fusion defects but also by skeletal (hand or foot) malformations. The etiologic heterogeneity of Mullerian fusion defects is considered.