The clinical, radiographic, and morphological findings in 25 cases of atelosteogenesis and boomerang dysplasia have been reviewed. The review confirms the nosologic grouping of atelosteogenesis type I with boomerang dysplasia and the clinical and radiographic overlap of features between atel- osteogenesis I and atelosteogene- sis II (synonymous with De la Chapelle dysplasia) and a group of patients with atelosteogenesis type III. A common pathogenesis is suggested for atelosteogenesis type I and boomerang dysplasia. A marked excess of male fetuses with boomerang dysplasia was observed. Atelosteogenesis type II shows distinctive chondro-osseous histopathology with a major disturbance in cartilage matrix macromolecules. An overlap of phenotypic, radiographic, morphological, and cartilage histochemical features with those observed in diastrophic dysplasia and achondrogenesis type IB suggests that atelosteogenesis type II has common pathogenetic features with disorders of sulfation of connective tissue matrix macro- molecules.