Previous genetic studies of idiopathic talipes equinovarus (ITEV) suggest an environmental and genetic component to the etiology of ITEV. The present study was undertaken to assess the role of causal factors in the development of ITEV. A total of 285 propositi were ascertained, with detailed family history information available in 173 cases and medical records on the remaining 112 propositi. Information was collected on specific prenatal, parental, and demographic factors. No racial heterogeneity was noted among any of the factors. The overall ratio of affected males to females was 2.5:1. The incidence of twinning among all propositi was significantly increased (P=0.006) above the expected population frequency. A family history of ITEV was noted in 24.4% of all propositi studied. These findings, in addition to the detailed analysis of 53 pedigrees with ITEV history, suggest the potential role of a gene or genes operating in high-risk families to produce this foot deformity.