In a randomized placebo controlled parallel double blind study on 40 patients suffering from venous edema in chronic deep vein incompetence, the edema-reducing effect of horse chestnut seed extract vs. placebo, being the main test variable, was demonstrated by hydroplethysmography to be statistically significant. In addition, measurements of leg volume under aggravated conditions (edema provocation) were conducted, which yielded the same results. Additional measurements of leg circumference tendentially confirm the demonstrated clinical efficacy of verum, as is true for phlebody-namometric measurements (pressure at rest, minimum pressure, replenishment time) as well. By measuring the leg volume before and after edema provocation, it could be shown that the clinical benefit for the patient is present in all everyday situations (in movement as well as on sitting or standing). Treatment with an edema protective agent of the horse chestnut seed extract type is thus a useful adjunct to compression therapy. The tested preparation were well tolerated.