The purpose of this study was to develop an optimal technique for greater saphenous vein distention during preoperative duplex assessment. An Acuson 128 scanner with a 7.5-MHz sector probe was used to assess the effects of venous occlusion and dependent position on the diameter of the greater saphenous vein in 20 male volunteers. The greater saphenous vein was imaged 10 cm above and 10 cm below the knee with the subject lying horizontal, horizontal with a thigh tourniquet inflated to 40 mm Hg, inclined at 15 degrees of reversed Trendelenburg, and inclined at 15 degrees of reversed Trendelenburg combined with the tourniquet inflated to 40 mm Hg. Maximal vein diameters and circumferences were measured by a sonographer blinded to the conditions of vein measurement to avoid interpretation bias. Using a t test assuming equal variances, the increases in vein circumferences and diameters achieved by dependency and tourniquet combined were significantly greater than those achieved by dependency alone (p=0.004). The technique of dependency combined with tourniquet inflation to 40 mm Hg facilitates greater saphenous vein imaging and provides an optimal method of venous distention.