The great variability of O-glycan structures makes their analysis a challenging task, which can be solved by the use of several complementary methods. While chromatographic analysis of the fluorescently labeled oligosaccharides shows the quantitative amount of the different glycans in comparison to a standard, mass spectrometry analysis of permethylated oligosaccharides allows identification of new or uncommon glycan structures. In combination with liquid chromatography, all structures present in one sample can be identified. The linkage of the monosaccharides can be analyzed by GC-MS after further derivatization of the permethylated glycans.