Angiogenesis is a fundamental component of complex biological processes, including oncogenesis. The aim of this work was to optimise and validate an ex-vivo angiogenesis assay as a quantitative (PC image) biological method for testing promising natural compounds and herbal drug preparations for their pro-/anti-angiogenic activity. The bioassay is based on the principle of wound healing and quantifies the effect of angiogenic agents on neovessel outgrowth of human placental vessels embedded in a three-dimensional fibrin matrix. The assay was validated by using known, well characterised pro- and anti-angiogenic effectors (basic fibroblast growth factor and carboxyamidotriazole, respectively), and an angiogenesis inhibitor of plant origin (green tea leaves extract) was used as a reference product to demonstrate the applicability of the assay for plant extracts. Other standardised plant extracts prepared from olive tree leaves and horse chestnut seeds were tested for their angiogenic potential, but showed only slight inhibitory or no activity, respectively. The results presented here indicate that this human ex-vivo angiogenic assay is "ready to use" for screening of herbal drug preparations and pure compounds.