Following the oral administration of tea catechins, (-)-epicatechin, (-)-epigallocatechin, (-)-epicatechin gallate and (-)-epigallocatechin gallate, respectively, to rats, the presence of these catechins in the portal blood was examined. It was confirmed by HPLC and mass spectrometry analysis that each of the administered catechins was present in the blood. These results clearly indicate that four predominant catechins in fresh tea leaves are absorbed, at least in part, into the rat portal vein.