The new lichen xanthones 2,5-dichloronorlichexanthone (in Buellia sp.), 2,7-dichloronorlichexanthone (in Buellia sp., Lecanora broccha), 4,7-dichloronorlichexanthone (in Lecidella asema) and 5,7-dichloronorlichexanthone (in Buellia sp., Lecanora broccha, Lecidella asema, Lecidella subalpicida) have been shown to co-occur in various combinations with the known naturally occurring xanthones 2,5-dichloronorlichexanthone, 4,5-dichloronorlichexanthone, isoarthothelin (2,5, 7-trichloronorlichexanthone), arthothelin (2,4,5-trichloronorlichexanthone), 4,5, 7-trichloronorlichexanthone (asemone), 5,7-dichloro-3-O- methylnorlichexanthone, 2, 5,7-trichloro-3-O- methylnorlichexanthone, 4,5, 7-trichloro-3-O-methylnorlichexanthone, and thiophanic acid. Although chemosystematic studies have had an enormous impact on lichen taxonomy, the majority of studies have focused on the occurrence and distribution of depsides, depsidones, and dibenzofuran derivatives. Even though they are widely distributed, xanthones have been less favored because of initial confusion in structural assignments and continuing difficulties in distinguishing the numerous (and often isomeric) compounds involved. However, these difficulties have now been largely overcome by high performance liquid chromatographic and mass spectrometric methodology (Culberson & Elix 1989) and the fact that the structural assignments have now been secured by the unambiguous synthesis of many lichen xanthones (Elix & Bennett 1990; Elix & Jiang 1990; Elix et al. 1978, 1990a,b; Fitzpatrick et al. 1980; Sundholm 1978, 1979). Moreover, the utility of these derivatives has recently been recognized and effectively employed in systematic studies of Lecanora (Leuckert & Poelt 1989) and Lecidella (Knoph 1990; Rambold 1989) lichens. In this paper we report the natural occurrence of a further four isomers of dichloronorlichexanthone in several lichen species.