Neurogenic claudication can be difficult to diagnose despite of strict radiologic criteria for lumbar stenosis. Because canal dimensions can change with body posture, and neuroimaging studies are usually done only in the supine position, not all patients with neurogenic claudication will have CT scan documented stenosis. This study evaluated changes in F wave minimal latency, chronodispersion and SEPs from the lower limbs after walking in normal thirteen subjects and twelve patients with lumbar spinal stenosis. In normal subjects, only F chronodispersion showed a significant decrease for both the peroneal and tibial nerves(p<0.05) after walking. Patients with spinal stenosis had markedly increased F chronodispersion in the peroneal nerve(p<0.01) but had minimal changes of the F minimal latency and SEPs. In conclusion, the marked changes of F chronodispersion after walking increase the diagnostic sensitivity in patients with spinal stenosis, who do not have abnormal nerve conduction and electromyographic findings.