The conventional methods of gas liquid chromatography or mass spectrometry failed to be useful for the identification of the biliary 3beta,7alpha-dihydroxychol-5-en-24-oic acid, a key intermediate of chenodeoxycholic acid biogenesis. It has been preliminarily reported that this acid in human bile was successfully identified by gas chromatography-mass spectrometry, after the methoxylation of its allyl alcohol group. Physical as well as spectral properties of the methoxylation products derived from the acid were reported, compared with those from its 7beta-epimer.