One hundred thirty-seven limbs with venous obstruction were analyzed. The arm/foot venous pressure differential and reactive hyperemia tests were found to be useful techniques to diagnose and grade venous obstruction. Traditional techniques including venography and ambulatory venous pressure are inferior in this regard. The newer techniques have provided newer insights in venous obstruction which are detailed herein. The hand-held Doppler was surprisingly very sensitive in grade I as well as in more severe forms of obstruction. Neither anatomic locale of obstruction nor its extent determined hemodynamic severity. Extensive proximal lesions could be hemodynamically mild, and conversely distal crural obstructions and single segment lesions could be hemodynamically severe. Phlebographic appearance was a poor index of collateralization. The paradoxical venous pressure response to the reactive hyperemia test in grade IV obstruction was found to be due to suppression or delay of the reactive hyperemia response itself in the presence of severe venous obstruction. The pain of venous claudication may be related to this phenomenon. Skin ulceration in the presence of venous obstruction was related to the associated reflux rather than the hemodynamic severity of the obstruction itself. The Linton procedure was found to be useful in treating such skin ulcerations. After perforator disruption, obstruction did not become hemodynamically worse, but reflux as measured by the Valsalva test improved with ulcer healing. The improvement in reflux related to Valsalva offers for the first time a hemodynamic rationale for the Linton procedure.