Abstract
A 28 year old woman presented a syndrome of slow spinal compression evolving over four and a half years at the level C1--C2 vertebrae due to a solitary osteochondroma of the posterior arch of the atlas which was excised by laminectomy. Radiographys of the skeleton did not show the presence of other osteogenic tumours. This is the fifth case of solitary osteochondroma to be published. Elsewhere, in six cases out of 14, the vertebral lesion formed part of generalised exostoses.