Quercetin, rutin, alphaG-rutin (a water soluble flavonoid), and a mixture of rutin and alphaG-rutin were administered to rats by a single gastric intubation, and their absorption and urinary excretion were examined. The plasma and 24 h urinary levels of aglycons (quercetin and tamarixetin/isorhamnetin) were measured by HPLC after deconjugation with beta-glucuronidase/sulfatase treatment. alphaG-rutin was absorbed more rapidly than quercetin or rutin, and the plasma concentrations of quercetin and tamarixetin/isorhamnetin reached the highest peak level 30 min after dosing. Quercetin, rutin, and the mixture of rutin and alphaG-rutin showed the first peak level 8 h, 8 h, and 30 min after dosing, respectively. The area under the concentration-time curve (AUC) for quercetin in rats administered alphaG-rutin was approximately 4.5- and 2-fold higher than those in rats administered quercetin and rutin, respectively, and was almost the same as that in rats administered a mixture of rutin and alphaG-rutin. The highest 24 h urinary excretion was observed in alphaG-rutin-administered rats. These results suggest that alphaG-rutin is absorbed more efficiently than either quercetin or rutin and that a high plasma concentration can be maintained by supplying rutin and alphaG-rutin in combination.