The syndromes associated with a narrow lumbar spinal canal are described and discussed. In thirteen cases two main groups were evident, the larger group having mainly backache and root pain, the smaller group having intermittent claudication. A method of recognising the narrow spinal canal on plain radiographs is described, and a comparison made with normal controls. The findings at operation are reported and the importance is emphasised of making a wide laminectomy for decompression. Our thanks are due to the neurosurgeons of the South-West Neurosurgical Unit, Mr G. L. Alexander, Mr D. G. Phillips and Mr A. Hulme, who kindly allowed us full use of their clinical notes. We would also like to thank Mr G. Banham for the reproductions, Mr E. Turnbull for the drawing and the secretarial staff for their patient co-operation.