OBJECTIVE Hemodynamic effects of compression devices in patients with venous insufficiency are still under dispute. The aim of this paper was to describe a method which is able to give quantitative results concerning an improvement of the venous pumping function by using compression devices in patients with venous insufficiency. METHODS The ejection fraction (EF) of the calf pump can be measured using strain gauge plethysmography proximal to a compression device on the leg and the degree of improvement depending on the exerted pressure and the elastic property of the material can be assessed. Experiments were carried out in 15 normal volunteers and in a total of 68 patients with severe superficial venous incompetence and who were investigated without compression and with various compression devices measuring interface pressure in different body positions. RESULTS Examples demonstrating the usefulness of the plethysmographic method are given. The median values of EF were 64.6 (IQR 63.4-68.6) in normal subjects and about half in the venous patients. Statistically significant improvement was achieved using inelastic bandages, resulting in further improvements with increasing pressures between 20 and 60 mmHg. Elastic stockings led only to a moderate improvement of the deficient venous pumping function. Significant correlations were found between EF and standing and walking pressure. CONCLUSIONS The described plethysmographic method is very useful to assess haemodynamic effects of different compression devices in patients with venous insufficiency.