Objectives: To describe the underlying causes, surgical results and prognostic factors in thoracic stenosis causing myelopathy. Methods: The underlying causes and surgical results were analyzed retrospectively in 28 cases of thoracic spinal stenosis which caused myelopathy. Degenerative spondylosis was the most common cause, and three cases were associated with systemic diseases. Decompressive laminectomy was performed in 24 cases, anterior decompression in ®ve cases, and combined decompression in one case. Ossi®cation of ligamentum¯avum was found in 18 cases, facet hypertrophy in 13, ossi®cation of posterior longitudinal ligament in six, and ventral spur in four. Postoperatively 16 patients improved and four patients worsened. Follow-up ranged from 2 months to 5 years and 8 months). Statistical analysis was performed using a w 2 test to investigate the relationship between subjects. Multivariant analysis (general linear model) was used to determine the factors which in¯uence surgical outcome. Results: There were neurological improvements in 16 patients, in whom Nurick grade changed from 3.3 preoperatively to 1.8 postoperatively. Eight patients showed no signi®cant change in functional grade and four patients deteriorated after decompressive laminectomy. The group of which initial symptom duration was less than 2 years showed better results (P=0.006). The group with sucient decompression and no additional proximal stenosis had better treatment outcome (P=0.005, P=0.002). Conclusion: Chronic severe myelopathy caused by thoracic spinal stenosis can be reversible with appropriate decompression. Surgical outcome was dependent on initial symptom duration, sucient decompression and presence of additional proximal stenosis.