Background: The contribution of biologically active non-nutrient chemicals to the health benefits of the Mediterranean diet is controversial because of their low dietary concentrations. Hydroxytyrosol is a dopamine metabolite, and also a very active naturally occurring phenol compound in olive oil. Aim of the study: To examine the disposition of hydroxytyrosol in humans, given that we discovered its presence in red wine in the frame of the study. Methods: The pharmacokinetics of hydroxytyrosol from two clinical trials, designed to assess the short-term and postprandial effects of moderate doses of wine and olive oil in healthy volunteers, were compared. Results: Despite a five-fold difference in the doses of hydroxytyrosol administered (0.35 mg for red wine and 1.7 mg for olive oil), urinary recoveries of hydroxytyrosol were higher after red wine administration. An interaction between ethanol and dopamine after red wine ingestion leading to the formation of hydroxytyrosol was observed. Conclusions: Biological effects after red wine ingestion should be re-examined on the basis of combined hydroxytyrosol concentrations from red wine and dopamine turnover. © Steinkopff Verlag 2006.