Pyridoxine 3, 4-dipalmitate (PIN-DP), insoluble in water, was little absorbed in man following oral administration of suspension in water or aqueous Tween 80. But, the absorption increased markedly with a solubilized solution with Tween 80. Previously, it was found that PIN-DP failed to permeate the intestinal tract unlike pyridoxine (PIN) which was the hydrolyzed product of ester in the tract. Hydrolysis of PIN-DP solubilized with Tween 80 increased ten times with the addition of sodium taurocholate or glycocholate. But, no increase was observed with the addition of sodium lauryl sulfate or bis (2-ethylhexyl) sulfosuccinate. PIN permeated through the everted sac of rat intestine following the addition of sodium taurocholate and lipase to a solubilized Tween 80 solution of PIN-DP.