Cacao polyphenols, catechins and procyanidins have attracted interest because of their possible effect on cardiovascular health. This paper provides an overview of our research on the effects of cocoa polyphenols on low-density lipoprotein (LDL) oxidizability and atherosclerosis. Polyphenol rich cocoa ingestion prolonged lag time (an index of LDL oxidative susceptibility) and decreased plasma oxidized LDL levels in humans and prevented atherosclerotic lesion formation in experimental animals. Catechins in cocoa show high bioavailability, and approximately 25-30% of ingested catechins are detectable in urine. After oral supplementation, they are present in blood as metabolites such as glucuronides and/or sulfate conjugated and/or methylated forms. The catechin metabolites (glucuronides) of rats and humans are structurally completely different, and their antioxidative activity is relatively maintained in rats but not in humans. On the other hand, ingestion of cacao products increased the level of HDL. The up-regulation of HDL might be shown antioxidative effect. Thus, cacao polyphenols may reduce cardiovascular disease risk.