In this study, Chinese gallotannins were characterized by MALDI-TOF MS, and effects of cationization reagents on the quality of spectra were investigated. The trideca- and tetradeca-galloyl glucoses were observed in Chinese gallotannins, which could not be detected in earlier studies. When Cs+ was used as the cationization reagent, Chinese gallotannins gave a relatively simple MALDI-TOF spectrum, three series of quasimolecular ions [M + Cs](+), [M + 2Cs-H](+), and [M + 3Cs-2H](+) and a series of metastable ion peaks with minimum abundance were detected. Selection of Na+ as the cationization reagent, additional three series of ion peaks including two patterns from the fragmentation and complex 2M adducts [2M + Na](+) can be distinguished. In the case of no deionization or addition of cationization reagent to the analyte/ matrix, naturally abundant Na+ and K+ as the cationization reagent, [M + Na](+) and [M + K](+) molecular ions both appeared in the complicated spectrum. Therefore, we conclude that cationization reagents affect the MALDI-TOF MS spectrum of Chinese gallotannins significantly. (c) 2007 Wiley Periodicals, fnc.