Aescin, the major active principle from Aesculus hippocastanum (Hippocastanaceae) the horse chestnut tree, has shown satisfactory evidence for a clinically significant activity in chronic venous insufficiency (CVI), haemorrhoids and post-operative oedema. In one controlled trial aescin was shown to be as effective as compression therapy as an alternative to medical treatment for CVI. The therapeutic benefit is well supported by a number of experimental investigations in different animal models, indicative of clearcut anti-oedematous, anti-inflammatory and venotonic properties, mainly related to the molecular mechanism of the agent, allowing improved entry of ions into channels, thus raising venous tension in both in vitro and in vivo conditions. Other mechanisms, i.e. release of PGF2 from veins, antagonism to 5-HT and histamine, reduced catabolism of tissue mucopolysaccharides, further underline the wide ranging mechanisms of the therapeutic activity of aescin. Aescin exists in two forms, α and β. β-aescin (b-escin) appears to be the active component of the mixture and is the molecular form present in major available pharmaceutical products. Beta-aescin has cytotoxic activity toward human colon adenocarcinoma cell lines.