An open study was carried out to assess, primarily, the safety and tolerability of Aesculus hippocastanum in the treatment of chronic venous insufficiency (CVI). Patients underwent 8 consecutive weeks of treatment and were asked to take one 50 mg A. hippocastanum tablet, twice daily. In total, 91 adverse events were reported, of which only four were rated as probably related to the study drug. Patients judged the tolerability of the study medication in the majority of the cases at visits 2 and 3 to be ‘good’ or ‘fairly good.’ Only two patients rated tolerability as poor at visit 3. For each of the symptoms investigated the difference in the median value between baseline and visit 3 was found to be statistically significant and both the ankle and lower leg circumference decreased. The majority of patients rated efficacy to be ‘very good’ or ‘good,’ with only 10 patients reporting no effect by the end of the study.