New cytokinin derivatives with high surface activity were developed for capillary liquid chromatography/frit-fast atom bombardment (FAB) mass spectrometry. Propionyl ester derivatives of cytokinin nucleosides and glucosides and benzylamine derivatives of cytokinin bases gave stronger [M + H]+ ion currents than the underivatized compounds. In trace analysis by selective reaction monitoring, low (fmole) detection limits were found. In qualitative analysis by B/E-linked scanning, the derivatives also gave more spectral information, owing to the presence of fragment ions, diagnostic for the sugar moieties of nucleosides and glucosides, not present in the spectra of underivatized compounds. THe proposed FAB method was used to identify and quantify 10 isoprenoid cytokinins in Arabidopsis thaliana, including free bases, nucleosides, nucleotides and glucosides.