Changes in the blood and liver B_6 Ievels after oral administration of pyridoxal (PAL) and pyridoxal-phosphate (PALP) (10mg/kg) to rabbit and rat were investigated. It was found that PAL and PALP were well and rapidly absorbed by oral route and appeared in the blood dominantly as 4-pyridoxic acid (PiA) in rabbit and as PAL in rat. Same patterns in the blood elimination process were evidenced in both PAL and PALP administration. Circulation experiments using rat intestine in situ as well as experiments by everted sac in vitro revealed that PAL was absorbed from upper small intestine and by part from stomach and PALP was hydrolysed in the intestine and absorbed as PAL. On the basis of these findings, the feature of bioavai-labilities of PAL and PALP as well as their absorption mechanisms are discussed. (Received July 7,1971)