To evaluate whether hemoglobin oxygen saturation and hemoglobin concentration of the leg are useful indicators for circulatory compromise in patients with lumbar spinal canal stenosis, we investigated the changes in the indices during level gait using reflectance spectrophotometry. Thirty-three patients with lumbar spinal stenosis were studied. Preoperatively, the hemoglobin oxygen saturation was greater in the 33 patients than in the control subjects. The indices increased in the control subjects more than those in the patients. Postoperatively, the increases in hemoglobin oxygen saturation were greater in the patients with lumbar spinal canal stenosis than before decompression and the hemoglobin concentration tended to approximate that in the control subjects. The results suggest these indices might be useful for monitoring disease severity in patients with lumber spinal canal stenosis. In addition to stenotic ischemia in the spinal canal, it is thought that the neurogenic intermittent claudication is secondarily caused by circulatory failure in the lower extremities attributable to the autonomic nervous dysfunction.