The term osteochondrodystrophy describes a developmental disease of the skeleton which produces many different clinical pictures. It is a defect, often familial, in the orderly growth of ossifying cartilage, which may result in almost complete arrest or in any degree of partial arrest of endochondral ossification. The resulting deformities will depend on what pattern the perverted cartilage growth follows. It may take the form of enchondromas remaining as multiple islands of cartilage cells within the epiphyses or shafts, of multiple cartilaginous exostoses (chondrodysplasia) in which outgrowths appear at the line of enchondral ossification between the epiphyses and diaphyses, of chondromas predominant on, if not limited to, one side or one limb (Ollier's disease)1or of a severe epiphysial disturbance in which the heads of the femurs are practically absent in most cases and there is marked kyphosis and dwarfism (Morquio's disease).2It seems likely that achondroplastic dwarfism is