Changes in venous haemodynamics were studied after administration of a single dose of 3 g Heptaminol Adenosine Phosphate (HAP) to 30 subjects with primary varicose veins. Strain gauge plethysmography was used to observe changes in venous volume and in maximal venous outflow, 1, 2, 3 and 4 h after dosing. A significantly greater reduction in these parameters was found after treatment with HAP compared to placebo, indicating an improvement in lower limb venous circulation.