Resveratrol has been widely investigated for its potential health properties, although little is known about its metabolism in vivo. Here we investigated the distribution of metabolic products of [3H]trans-resveratrol, following gastric administration. At 2 h, plasma concentrations reached 1.7 % of the administered dose, whilst liver and kidney concentrations achieved 1.0 and 0.6 %, respectively. Concentrations detected at 18 h were lower, being only 0.5 % in plasma and a total of 0.35 % in tissues. Furthermore, whilst kidney and liver concentrations fell to 10 and 25 %, respectively, of concentrations at 2 h, the brain retained 43 % of that measured at 2 h. Resveratrol-glucuronide was identified as the major metabolite, reaching 7 microm in plasma at 2 h. However, at 18 h the main form identified in liver, heart, lung and brain was native resveratrol aglycone, indicating that it is the main form retained in the tissues. No phenolic degradation products were detected in urine or tissues, indicating that, unlike flavonoids, resveratrol does not appear to serve as a substrate for colonic microflora. The present study provides additional information about the nature of resveratrol metabolites and which forms might be responsible for its in vivo biological effects.