Cases have been reviewed and described to show that kyphosis of the vertebral column may follow tetanus, with or without demonstrable fracture of the vertebral bodies. The force initiating this deformity is explained on the basis of the contraction of certain muscle groups during tetanic convulsions. Although there is a greater tendency for vertebral fracture to occur in adults, the majority of post-tetanic kyphoses occur in adolescents in an age group corresponding to that of juvenile kyphosis. The similarity to juvenile kyphosis includes also the clinical and roentgenographic characteristics of both conditions, with the exception of the level of the deformity, and this difference is explained by the "dynamic" level of stress in post-tetanic kyphosis in contrast to the "static" level of stress in juvenile kyphosis. Post-tetanic spinal deformity in adults is the result of a particularly severe and prolonged attack of tetanus. Because it does not seem possible to explain the occurrence, age incidence, and roentgenographic changes in adolescents purely on the basis of the intensity of tetanic convulsions, and because of the striking resemblance to juvenile kyphosis, a common factor of weakness in certain adolescent spines is sought to explain this. Further study has indicated that this factor, most prominent in juvenile kyphosis, is an overacceleration of endochondral ossification during the periods of most active body growth, causing ossification in the metaphyses of the vertebral bodies to lag behind a predominating proliferation of columnar cartilage.