Within the framework of a case observation study involving more than 800 general practitioners, more than 5,000 patients with chronic venous insufficiency (CVI) were treated with standardised horse chestnut extract and followed up at regular intervals. The evolution of the symptoms, tolerability and adverse drug reactions were recorded. All of the symptoms investigated-pain, tiredness, tension and swelling in the leg, as well as itching and the tendency towards edema-all improved markedly or disappeared completely. The results of this study show that rational treatment with horse chestnut extract represents an economical, practice-relevant therapeutic "pillar", which in comparison with compression has the additional advantage of better compliance.