Chondrodysplasiae with mesomelic predominance, that is with an elective defect of the middle segment of the limbs, constitute a complex group. The authors pronose to divide it into two types according to the presence or the absence of lesions in bones of the hand. The chondrodysplasiae without impairment of hands and feet include dyschondrosteosis, the type with cubitus and fibula hypoplasia described by Langer, Reinhardt and Pfeiffer's type with dominant transmissions, as well as the types with a relative elongation of fibula. The group of dysplasias in which hands and feet are concerned includes the dyschondrosteosis with shortness of hand, the acromesomelic dwarfism with impairment of phalanxes, described by Campailla and Martinelli, Nivegelt's syndrome, and the dwarfism with disorder in the vertebral segmentation, described by Robinow.