Vascular ultrasonography has an important role in the diagnosis and management of venous disease. The venous system, however, is more complex and variable compared to the arterial system due to its frequent anatomical variations. Thus, the aim of our study was to assess the great saphenous vein and superficial femoral vein at different levels and its relation to age, sex and body mass index in Egyptian population by noninvasive colored duplex ultrasound. Methods: Our study was cross- sectional descriptive study comprised 75 subjects with one hundred fifty- limbs. We classified studied subjects to lean and obese group according to body mass index (BMI). The diameter of the greater saphenous vein and femoral vein in mm were measured with duplex ultrasound longitudinal imaging in three different levels.at both lower limbs and in standing as well as supine position. Results: Obese patients had significantly higher diameter (mm) of the femoral vein compared to lean controls. However, the diameter (mm) of great saphenous vein of the both lower limb in the different levels (1 st Standing,2nd Standing 3 rd Standing 1 st Supine 2 nd Supine and 3 rd Supine) were non-significantly higher in obese women compared to lean subjects. Moreover, there were significantly higher diameter (mm) of great saphenous vein at 1 st Standing,2nd Standing 3 rd Standing in both lower limbs compared to corresponding levels in Supine position. By using ROC curve test, we found that the highest area under the curve (AUC) (0.797, C.I 0.669 - 0.924), sensitivity (96.1%) and specificity (63%) were of femoral vein diameter (mm) with cutoff (7.15 mm). linear regression analysis test found that, the diameter of femoral vein (mm) was only independently correlated with BMI. Conclusion: obese subjects had significantly higher diameter (mm) of the femoral vein compared to lean control. However, the diameter (mm) of great saphenous vein of the both lower limb in the different levels were non-significantly higher in obese women compared to lean subjects.