A rational selection of a restricted set from fifteen available chromatographic systems for the separation of flavonoids and phenolic acids identified in the methanolic extract ofRhamni cathartici fructusis discussed. Series of mathematical techniques for the evaluation of solvents and solvent combinations in thin-layer chromatography of flavonoids and phenolic acids have been investigated. The chromatographic systems are classified according to their mutual resemblance by numerical taxonomy techniques. The selection criterion in the groups, obtained by numerical taxonomy classification, is the information content or discriminating power. The numerical taxonomic and information theoretical selection procedures are compared and their respective advantages and disadvantages discussed.