The purpose of this review is to present current information on the natural course of lumbar spinal stenosis. As the population becomes older this condition is encountered more frequently. The diagnosis accuracy has improved and the number of cases detected is increasing intemationally. Because of the relative unpredictability of surgical treatment, good knowledge of natural evolution and of the predictive factors influencing the course of the disease is crucial. Unfortunately, and in contrast with numerous surgical series few studies have dealt with natural evolution. In addition to anecdotal reports, a few non randomized studies will be reviewed. Only one randomized study has compared shortand long term results of medical versus surgical treatment. Most of these studies are retrospective, with methodological flaws and are difficult to compare. At the present time no scientifically based recommandations can be made to LSS. patients at diagnosis. Similarly predictors of success of medical and surgical treatment still need to be identified. However results of the studies analyzed in this review suggest that a substantial proportion of patients do not automatically deteriorate and will remain unchanged or even improved by medical means. They also suggest that patients with severe baseline symptoms, block stenosis and degenerative spondylolisthesis tend to require surgical decompression. Randomized studies with the necessary ethical precautions are needed to obtain clear-cut conclusions.