A total of 1583 limbs in 878 patients who presented with symptoms of chronic venous insufficiency of the lower limbs were examined in the vascular laboratory. The anatomic distribution of valvular insufficiency was determined by continuous-wave Doppler ultrasound and functional severity was determined by the venous refilling time (VRT) using photoplethysmography. Severity of reflux was assessed using a four-class grading scale (classes 0 to 3) based on clinical and VRT criteria. A mixed incompetence of the valves in the superficial system and the perforators was encountered in the majority of patients (44% in class 0 and 85% in class 3). Deep vein incompetence was less common and usually consisted of isolated proximal incompetence of the common femoral vein (up to 32% in class 3) or was of a mixed type (21% in class 3). Isolated distal deep vein incompetence was uncommon. Proximal femoral vein incompetence and superficial system incompetence at the saphenofemoral junction were associated with severe reflux. There was significant improvement in the VRT in patients with more severe reflux (class 2 or 3) after application of an ankle tourniquet. Symptoms of moderate to severe chronic venous insufficiency and ankle ulceration may be a result of long-standing superficial system incompetence rather than deep venous disease and may thus be amendable to simple saphenofemoral ligation and interruption of perforators.