A new human in vitro anti-angiogenesis assay was established and applied to identify novel angiopreventive agents. Subsequently, two chemopreventive compounds, xanthohumol (XN) from Humulus lupu-lus L. (hop) and sulforaphane (SFN), an isothiocyanate derived from cruciferous vegetables (Brassicaceae), were selected for detailed in-vestigation of their angiopreventive potential and mechanisms invol-ved in the inhibition of angiogenesis. Representative targets included effects at the transcriptional levels of pro-angiogenic factors, anti-gelatinolytic and anti-endothelial activity. In vivo, XN was shown to exhibit a strong anti-tumour potency on human breast cancer xeno-grafts mediated by the inhibition of tumour-induced angiogenesis. These findings strongly suggest that XN and SFN represent attractive chemopreventive lead structures possessing a remarkable potential to prevent tumour development.