Idiopathic clubfoot is an uncommon congenital deformity that clusters in families but does not fit typical Mendelian inheritance patterns. Studies done on twins, different incidences in various ethnic groups, and transmission between generations all suggest a genetic component to clubfoot causation. Complex segregation analysis strongly supports the hypothesis that one major gene is responsible for a large portion of the risk for having a clubfoot. A few studies suggest an environmental causation of clubfoot, but are not persuasive. Clubfoot may be etiologically and/or genetically heterogeneous resulting in its complex inheritance pattern. Alternatively, idiopathic clubfoot may require a predisposing gene acting in a particular background of polygenes or environmental influences. Discovery of the cause or causes of clubfoot will provide improved genetic counseling and the potential for improved treatment, and insights into normal foot and leg development.