Achondrogenesis is a lethal skeletal dysplasia in which micromelia is severe and delay in ossification is extreme. The roentgenographic features are diagnostic and form a distinctive pattern. Almost total absence of ossification is noted in the vertebral bodies, sacrum, ischial and pubic bones, and calcaneus and talus. The shape of the ilia is distinctive. The condition may be differentiated from thanatophoric dwarfism and the other short-limbed types of dwarfs. Histologically, enchondral ossification is strikingly disorganized and matrix is lacking between the resting cartilage cells. Achondrogenesis is probably an autosomal recessive disease.