Pedigree analysis in this kindred is compatible with an autosomal dominant inheritance. The parents and three other family members have clinical and radiological features of dyschondrosteosis. The two propositi, a boy and a girl, have mesomelic dwarfism and hypoplasia of the mandible, ulna, and fibula. It is our interpretation that mesomelic dwarfism is the clinical manifestation of the homozygous state for dyschondrosteosis. Mesomelic dwarfism is character¬ ized by short stature caused primarily by reductions in middle segments of the extremities. There are varying skeletal abnormalities as¬ sociated with it, some of which were reviewed by Bailey.1 Langer2 de¬ scribed a type of mesomelic dwarfism with hypoplasia of the mandible, ulna, and fibula. We would select his description as prototype for the chil¬ dren discussed here and would refer to this type of mesomelic dwarfism as the Langer type.Dyschondrosteosis, on the other hand, is a term applied to individ¬ uals who have relatively attenuated