Resveratrol is a trihydroxystilbene present in certain red wines. It may play a role in the inhibition of lipoprotein oxidation and platelet activity. We have developed the first method to measure resveratrol in animal and human samples and to study its incorporation in vitro. After adding epicoprostanol as an internal standard, samples are subjected to lipid extraction in the presence of antioxidant and under dim light to minimize both denaturation and isomerization of the trans-resveratrol to the cis-form. Extracts were purified by cold acetone precipitation and the resveratrol-containing acetone phase was evaporated under nitrogen. The resveratrol was analyzed as a trimethylsilyl derivative by capillary gas chromatography which resolved the cis- and trans-resveratrol (6.6 and 12.9 min, respectively). Analyses of samples spiked with pure trans-resveratrol (0.1 to 10 microg) indicated that the method was specific and gave excellent linearity and recovery (96.8%) with a high reproducibility (coefficient of variation: 3.3%). The detection limit was about 50 ng/ml. Applications show that resveratrol was incorporated into blood cells and lipoproteins after in vitro incubations with plasma, lipoproteins and cells.