GAG samples have been successfully ionized using electrospray ionization (ESI) techniques. Due to the production of multiply charged ions and a reduction of overall mass-to-charge ratio, the visualization of larger macromolecules by ESI is possible. FT-ICR MS has been shown to be a powerful took for structural analysis of GAGs. Both threshold and electron activation techniques can be used for the analysis of GAGs, however electron based methods have been shown to be more successful. Negative electron transfer dissociation (NETD) and electron detachment dissociation (EDD) are both powerful methods for producing abundant cross ring fragments. Electron detachment is achieved by bombarding multiply charged negative ions with electrons of a moderate kinetic energy (15-20eV). Fragmentation can occur from radical-species produced by electron detachment, or from electronically-excited precursor ions. The combination of these two pathways produces rich and complex mass spectra whose analysis can provide a great deal of structural detail. NETD and EDD are both available on our FT-ICR MS instruments. Electron based methods produce both glycosidic and cross-ring fragments, allowing for the identification of modifications such as sulfation, N-acetylation, and C-5 stereochemistry.