Centaurium erythraea Rafn. (Gentianaceae) is a folk medicinal herb whose underground parts have not been previously investigated. We report here that the n-hexane extract of the roots contains six 1-hydroxy-3-methoxyxanthones identified by their spectral data and those of the acetylated derivatives. They are, in order of elution from the silica column, 1,8-dihydroxy-3,5-dimethoxyxanthone (methylbellidifolin), 1,8-dihydroxy-3,5,6,7-tetramethoxyxanthone (8-desmethyleustomin), 1-hydroxy-3,5,6,7-tetramethoxyxanthone, 1-hydroxy-3,5,6-trimethoxyxanthone, 1-hydroxy-3,7,8-trimethoxyxanthone (decussatin), and 1-hydroxy-3,5,6,7,8-pentamethoxyxanthone (eustomin). With the exception of methylbellidifolin and 8-desmethyleustomin, the other xanthones found in the roots of C. erythraea have not been previously reported from the aerial parts of this species. When the xanthonic compositions of C. erythraea aerial parts and roots are compared, on the basis of the identified compounds, it is clearly shown that three oxygenated derivatives (tetra-, penta-, and hexaoxygenation) were obtained from both aerial and underground parts, that hexaoxygenated compounds are the most abundant in both, and that aerial parts generally contain more hydroxylated compounds than roots. In the family Gentianaceae, the genus Centaurium is characterized by xanthones with a single aromatic ring (1-OH, 3-OMe), by the absence of the usual trioxygenation in favor of a new oxidative step, hexaoxygenation, previously found only in the genus Eustoma, and by the xanthone compound 8-desmethyleustomin, only found previously in Centaurium cachanlahuen, C. erythraea, and Centaurium lrnarifilium.