Several ways of using the recently developed high-performance thin-layer chromatography (HPTLC) precoated plate NH2 F 254s to separate purines and pyrimidines are described. This precoated plate is coated with silica gel 60 which has been chemically modified with alkylamino groups. In view of the chemical properties of the functional groups bonded to the silica gel matrix, the HPTLC precoated plate NH2 F 254s can be considered to be a weak basic ion-exchange plate. In aqueous eluants the substances are separated principally according to charge differences. The HPTLC precoated plate NH2 F 254s can, however, also be used to separate uncharged, polar compounds with organic solvents. Examples of separations and chromatograms for its use in both aqueous and organic eluants are given.