Neurologic problems caused by vertebral stenosis in the thoracolumbosacral (TLS) region are common in achondroplasia. Surgical decompression by means of laminectomy is recommended often, but its long-term results have not been assessed. We reviewed the clinical history of 22 achondroplastic patients who had at least one TLS laminectomy performed before 1981. Symptoms predated the first TLS laminectomy by a mean of 2.3 years (range 0.1-17 years). Preoperatively, 91% of patients had motor function impairment, 86% had sensory dysfunction, 86% had neurogenic claudication, 77% had radicular pain, 59% had symptomatic bladder dysfunction, and 32% had fecal incontinence. Only upper motor neurons were affected in 45%, only lower motor neurons in 27%, and both in 27%. Follow-up after the first TLS laminectomy averaged 8 years. Of the 20 patients who initially improved neurologically, 12 had functional improvement for more than 5 years. However, 11 of these 12 subsequently regressed and 10 had additional laminectomies. Long-term neurologic and functional improvement was associated with both a short duration of symptoms preoperatively and absence of cervical stenosis. Because of hypertrophic scarring, 9 patients developed compression at the site of the initial TLS laminectomy and required re-operation 6.4 years (range 1-11 years) later. We conclude that TLS laminectomy is an effective treatment for spinal stenosis if performed early in the course of the neurologic syndrome. However, some patients have, or later develop, compression adjacent to the myelographic site of stenosis, and some develop hypertrophic scarring at the site of initial decompression. We therefore suggest that the first TLS laminectomy extend (1) 3 levels cephalad to the myelographic block, (2) at least to S2, and (3) laterally at least to the facets.