The venous pressure in the ascending lumbar vein was measured by catheter and pressure transducer to document venous stasis in degenerative lumbar spinal canal stenosis. Measurement of the pressure in the ascending lumbar vein at rest revealed a progressive rise of the mean pressure from the control group to the lumbar intervertebral disc herniation group, and the lumbar spinal canal stenosis (LSCS) group in ascending order. Pressure curve tracings showed a plateau accompanying increased abdominal pressure during the Valsalva maneuver. Phase 3 was defined as the recovery period of decreasing pressure which began with the release of abdominal compression and terminated with the return to the initial pressure. The duration of phase 3 was prolonged in LSCS (p less than 0.01). It followed that the prolonged phase 3 documented the existence of venous stasis and its extent in LSCS. It is conceivable that increased venous pressure in the lumbar vertebral venous plexus participates in the pathogenesis of cauda equina claudication in LSCS.