1. A left-sided, paravertebral, hour-glass tumour causing destruction of the neural arches of the third and fourth thoracic vertebrae with evidence of spinal cord compression, is described. The tumour presented the typical histological appearance of a chondroblastoma.

2. The intraspinal part of the tumour was excised and the mediastinal part curetted. Post-operative radiotherapy was given. The patient was symptomless two years after operation.

3. No example of Codman's tumour with similar features and in such a situation has been described before in the literature. Pathological, clinical and radiological aspects of chondroblastomata are briefly discussed and some remarks concerning their treatment are added.