The article reports on twenty patients with thoracic prolapsed discs treated by surgery within a period of ten years. The incidence in relation to prolapses at all levels was 1.2%. The average age was 50.3 years and there was no definite sex predominance. The segments Th 10-11 and Th 11-12 were the preferred sites. The period of the disease varied from a few hours to nine years. Among the most frequent subjective complaints were radiating pain, paraparesis of the legs and disturbed micturition. A definitely traumatic cause of the disease was present in one case only. Besides exact neurological diagnosis it is imperative to effect myelography with positive contrast medium, revealing the typical circular or oval-shaped filling defects. In our patients, laminectomy was performed 17 times, and hemilaminectomy three times. Besides removal of the prolapse, the dentate ligament was always divided. In some cases we also performed rhizotomy. Operation improved 15 patients, whereas in two patients the condition got worse and three patients showed neither improvement nor deterioration.