Chronic venous stasis is an extremely complex clinical syndrome of pain and changes in the skin that can involve the superficial, deep, and perforating veins. This syndrome is commonly referred to as "the postphlebitic syndrome," implying that thrombophlebitis is its sole etiology. To test this hypothesis, we performed ascending venography on 51 limbs of patients with the chronic venous stasis syndrome and demonstrated that 32 had no radiological evidence of recent or old thrombophlebitis. Instead, they had normal-appearing veins, suggesting primary incompetence of the deep and/or perforating venous valves rather than thrombophlebitis as the etiology. Since various operations have recently been proposed to correct or bypass malfunctioning valves, precise demonstration of pathological change is required to choose the appropriate procedure and to evaluate results. Descending venograms were combined with the ascending studies in 42 limbs for this purpose. In addition to outlining the abnormalities responsible for chronic venous stasis syndrome in individual cases, interesting conclusions regarding the syndrome itself were reached.