The mass spectra behaviour of five 10-alkylthiocolchicine derivatives has been studied using electron ionization and MALDI-TOF MS techniques. Fragmentation patterns of colchicines derivatives after EI have been investigated, as well as mass spectra after collision-induced dissociation (CID) MALDI have been used to gain structural information. To the best of our knowledge, this is the first time that the MALDI MS/MS data for colchicine and its alkylthio derivatives have been described. It has been shown also that the data derived from mass spectra can be used for identification/quantitative determination of natural and modified alkaloids of colchicine group. The detailed fragmentation pathways proposed here could be helpful for the characterization of other colchicines of these type. The utility of different ionization techniques for analysis of compounds of this class has been evaluated. Due to the cytotoxic activity towards tumour cell lines, 10-alkylthiocolchicines may be considered as the active ingredients of anticancer agents. If these compounds find use in medical treatment, their distribution in organism and their metabolism will have to be monitored by spectroscopic or spectrometric methods. The characteristic fragment ions may be used by Selected Reaction Monitoring method for determination of colchicine analogues.