Hereditary theory was first proposed by Joachimsthal in 1905. However, a family history of congenital muscular torticollis is uncommon. This is a report of two female children who are interrelated and have congenital muscular torticollis. They are sisters. No environmental factor could be identified that would predispose the the children to congenital muscular torticollis. In this family, it is apparent that genetic factors are influencing the development of this condition. The cause of congenital muscular torticollis is unknown, but heredity may play a more important role than has previously been supected.