Several population studies have described the incidence and prevalence of chronic venous disease (CVD). This prospective study was designed to determine in detail the distribution of reflux and obstruction in all lower limb veins to provide reference data for the management of CVD patients. Consecutive patients presenting to a university vascular clinic and undergoing a duplex ultrasound examination were included in the study. Patients with C2 CVD class or higher regardless of symptoms or cosmetic concerns were evaluated. Every patient received a detailed history and physical examination by a vascular surgeon including all demographic information. All patients then had a bilateral lower extremity venous ultrasound examination for reflux and obstruction. The examination was performed in the standing position with the exception of iliac veins and inferior vena cava, which were assessed in the supine position. Location and extent of reflux, vein diameters, and presence of obstruction were recorded. Obstruction was characterized as partial or complete for each venous segment. History of objectively documented venous thrombosis and findings on ultrasound examination indicating previous thrombosis were noted. There were 491 patients who presented for evaluation. Excluded were 241 patients, of whom 49 had undergone previous treatment and 192 had only C0 or C1 disease bilaterally. The remaining 250 patients were 32.8% male and 67.2% female. The mean body mass index was 28.3 kg/m2 (range, 19.2-44 kg/m2); 55.2% identified as white, 11.2% as black/African American, 23.6% as Hispanic/Latino/Spanish origin, and 0.8% as American Indian/Alaska Native. Asymptomatic patients accounted for 17% of the cohort and symptomatic patients for 83%. Clinical, Etiology, Anatomy, and Pathophysiology (CEAP) class was distributed as 43% C2, 28.8% C3, 15.2% C4, 7.6% C5, and 4.8% C6. In the superficial veins, 70.4% of patients had only unilateral disease; 29.6% had bilateral disease. Axial reflux was found in one vein 53.2% of the time; two veins, 27.6%; three veins, 4.8%; four veins, 4%; five veins, 0.8%; and six veins, 0.4%. Calculation of potential ablations was performed, excluding superficial reflux in 2.6% of limbs with small diameter, 5.6% with segmental reflux, 4.4% with tributary reflux, and 6.0% with nonsaphenous reflux that would receive adjunct procedures including microphlebectomy or ultrasound-guided foam sclerotherapy. These adjunct procedures would account for 18.6% of therapy, whereas 64.0% would be ablative therapy. Past deep venous thrombosis was found in 7.2%; 2.8% had concurrent superficial and deep venous thrombosis. From these data, we can assume that the average patient presenting with venous complaints would have symptomatic disease with great saphenous vein reflux and would require one or two ablations based on the prevalence of saphenous reflux in the population. Patients who had at least one saphenous vein with reflux would have an average of 1.6 ablations/patient.