The roots of Canscora decussata Schult has been shown to contain sixteen xanthones (I-XVI), six of which (II, VII, IX, XII, XIII, XVI) are previously unreported in nature. Chemical and spectral methods and in most cases comparison with authentic synthetic samples established their identity as mangiferin (I), 1,5-dihydroxy-3-methoxy- (X), 1-hydroxy-3,5-dimethoxy- (VII), 1,3,5-trihydroxy-6-methoxy- (II), 1,3,8 trihydroxy-7-methoxy- (III), 1,8-dihydroxy-3,7-dimethoxy- (XI), 1-hydroxy-3,7,8-trimethoxy- (VIII), 1,3,8-trihydroxy-6,7-dimethoxy- (XIII), 1,8-dihydroxy-3,6,7-trimethoxy- (XII), 1-hydroxy-3,6,7,8-tetramethoxy- (IX), 1,3,5,6-tetrahydroxy- (XIV), 1,3,7,8-tetrahydroxy- (XV), and 1,3,6,7,8-pentahydroxy- (XVI) xanthones. In addition, three minor xanthones (IV-VI) have been isolated from the same source and are partially characterized. Biogenetic and chemotaxonomic significance of the co-occurrence of mangiferin and the other aforementioned xanthones in a single plant species such as C. decussata is discussed.