Mass spectrometry is essential for the structure determination of naturally occurring glycosides. Molecular weight and sugar sequence information can be obtained. Development of “soft” ionization techniques has allowed a direct mass spectrometric investigation of underivatized glycosides. Numerous different and complementary methods of ionization have been used for their study. For a given compound, the choice of a particular technique is crucial in order to obtain the structural information needed. A brief survey of these ionization techniques is given, together with examples of their use in major classes of plant glycosides.