Puerarin (an isoflavone C-glucoside from kudzu root) has been the focus of several studies investigating its potential effects on health benefits. In this study, we determined single dose tissue distribution of puerarin and its metabolites in order to examine whether they undergo selective uptake by specific organs. Puerarin was administered orally (50 mg/kg) to rats and the concentration of puerarin in tissue compartments was determined using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Puerarin was widely distributed in rat tissues with highest concentrations in lungs (799±411.6 ng/g wet tissues). In addition, we examined the excretion of puerarin into the bile. LC-MS/MS analysis of bile samples collected after infusing puerarin directly into the portal vein indicated that puerarin was excreted into the bile predominantly in the form of unconjugated puerarin. This report identifying puerarin in several organs including kidney and pancreas may explain its beneficial effects in diabetes. © 2008 Elsevier GmbH. All rights reserved.