We describe 2 unrelated families with male-to-male transmission of Nager syndrome. All 5 affected individuals have moderate expression of the phenotype. One affected boy also has Hirschsprung disease. Although Nager acrofacial dysostosis usually occurs sporadically, both recessive and dominant inheritance have been suggested on the basis of reported familial cases. The 2 families described here with father-to-son transmission strongly support the hypothesis that some cases of Nager acrofacial dysostosis occur in individuals who are heterozygous for dominantly expressed, autosomal mutations.