Despite a diet rich in saturated fatty acids, mortality rates in coronary heart disease (CHD) are relatively low in France. An explanation for this French paradox may be the high average level of red wine intake by its population. A negative correlation between the risk of mortality from CHD and the intake of flavonoids, a prominent component of red wine, has been suggested. This may be partly explained by the influence of these flavonoids on blood platelet aggregation.To find out whether ethanol is an essential component for the inhibitory effect of red wine on blood platelet aggregation we developed an alcohol-deprived equivalent (0.25 promillage ethanol). We investigated the potency of red wine, its alcohol-deprived equivalent, red grape juice and 12% ethanol on platelet aggregation in vitro in a dose-response experiment. As an agonist of platelet aggregation ADP was used.Red wine and its alcohol-deprived equivalent were equally potent in inhibiting platelet aggregation, whereas 12% ethanol had no effect. The inhibitory effects expressed as percentage decrease of platelet response are depicted in a table. Moreover, red wine and its alcohol-deprived equivalent are much more potent in inhibiting platelet aggregation than red grape juice.From this study in vitro, it is inferred that the flavonoids, not ethanol, present in red-grape-derived beverages are of major importance in inhibiting platelet aggregation and that fermentation processes may be an essential prerequisite for this effect.