Some recent studies have put forward the hypothesis that the presence of trans-resveratrol (trans-3,5,4'-trihydroxystilbene) in red wine may be related to some of its therapeutic properties. A fundamental step in view of this evaluation is the development of a method for the quick, accurate and precise analysis of this compound. Sample enrichment and purification can be obtained by solid-phase extraction using reverse-phase C18 cartridges. HPLC analysis carried out by means of a photodiode-array detector, with an internal standard method, allows the detection of up to 10 micrograms/L in wine, with a linear range between 0.6 and 300 ng injected and a precision of 3.3%. The results of the first analyses show that the concentrations of trans-resveratrol in wines might be much higher than so far reported in the literature.