The operative results in 37 consecutive patients suffering from developmental stenosis of the lumbar spinal canal, compared with those in spondylosis and disc herniations, are discussed. The diagnostic certainty of stenosis, suspected on the bases of clinical and radiographic data, is reached only at the operating table. To judge the usefulness of the operation we have considered not only the patients' verdicts, but also the improvements in neurological signs and the appearance of new deficits. Satisfactory results are around 80%, slightly less good with stenosis than with the other causes of lumbar syndrome. Radiographic study with contrast medium is mandatory. Dimer-X has been used with very clear radiographic findings and very few complications. Operating technique is also described: a wide laminectomy with facetectomy is advised. The great importance of early physiotherapy is emphasized.