Methods of glycosylation analysis are described in which a sample containing one or more specific oligosaccharide(s) (the analyte) is contacted with a surface on which is immobilized a glycosidase specific for the analyte and/or a specific binding partner for a product of the action of a glycosidase on the analyte. The surface may be the active surface of a biosensor, e.g., a biosensor based on the principle of frustrated total reflection.