Kyphotic deformity arising from failure of the formation of a vertebral body is described in nine patients. The study of the natural history demonstrates the progressive nature of this disorder resulting in severe deformity and neurological embarrassment. Early radiological recognition of this congenital deformity is essential and tomography is important in the early assessment. Tomography combined with myelography is essential to delineate the extent of bony abnormality and cord compression in severe kyphosis in order that adequate decompression and reconstructive surgery can be performed.