The isolation and identification of seven xanthones from an extract of the rhizomes of Iris nigricans is described. The isolated compounds are the xanthones, 1,3,6,7-tetrahydroxy-l,6,8-trihydroxy-2-methoxy-l,6-dihydroxy-3,7-dimethoxy- and 1,3,5,8-tetrahydroxy-, and the xanthone C-glycosides mangiferin, 7-O-methylmangiferin and a new compound 2-//-D-glucopyranosyl-l,3,5,8-tetrahydroxyxanthone (nigricanside). The new structure was established by detailed spectral and chemical analysis.