The availability of biomarkers that allow the estimation of the intake of specific foods and dietary components, as an alternative or addition to self-reported dietary questionnaires, could greatly enhance the effectiveness of nutritional research. The aim of the present study was to assess tartaric acid, one of the major components of red and white wines, as a potential biomarker of wine consumption. A total of twenty-one healthy men participated in a randomised cross-over feeding trial. They consumed a single dose of 100, 200 or 300 ml wine at dinner. Before each intervention, the participants followed a 7 d washout period during which they avoided consuming wine or grape-based products. Morning urine was collected and analysed by liquid chromatography coupled to electrospray ionisation tandem MS. A strong significant correlation was found between wine intake and urinary tartaric acid (r s= 0·9220; P <0·001). Using a cut-off value of 8·84 μg/mg creatinine, tartaric acid allowed wine consumers to be differentiated from non-wine consumers. The results suggest that urinary tartaric acid may be a sensitive and specific dietary biomarker of wine consumption.