Circulation disturbances in the cauda equina and nerve roots have been implicated in the genesis of neurogenic intermittent claudication (NIC) in patients with lumbar spinal stenosis (LSS). We report the clinical results of lipoprostaglandin E1 (lipo-PGE1) treatments in patients with NIC. Lipo-PGE1 was administered intravenously for 10 consecutive days to 40 patients, 31 of whom showed a response to the treatment. Of the clinical symptoms examined, walking ability and leg numbness were significantly improved with an average effective period of 2.5 months. However, patients with radicular pain and severely affected patients did not respond well. Nerve root circulation in eight patients who subsequently underwent surgery was measured with a laser Doppler flowmeter. We observed increased blood flow in seven of these eight patients, after the intraoperative administration of lipo-PGE1. Lipo-PGE1 produced symptomatic improvement for a limited period in the treatment of NIC associated with LSS. The drug appeared to exert its effects through an increase in the circulation of blood in the nerve roots and the cauda equina.