Metatropic dysplasia is a neonatally manifest entity that is characterized clinically by a rapidly progressing kyphoscoliosis leading to severe shortening of the originally long trunk ("metatropism"). Major radiographic features include flattening and defective ossification of the vertebral bodies, a narrow thorax and a marked hypoplasia of the basilar portions of the ilia with crescent-shaped iliac crests. There is some evidence of genetic heterogeneity. From five personal observations and from a review of the literature we conclude that metatropic dysplasia comprises at least three genetic entities: (1) a nonlethal type with autosomal recessive transmission; (2) a nonlethal dominant type and (3) a lethal type with death before or shortly after birth and possibly autosomal recessive inheritance. A careful clinical and radiologic analysis permits their classification and differentiation from similar, not yet well-delineated disorders. Attention is also drawn to the possibility of atlanto-axial instability in metatropic dysplasia which may cause severe neurologic defects.