This chapter contains sections titled: Introduction – Glycosylated Proteins Basic Building Blocks of Glycosylation in Human Cells Formation of Complex Glycan Structures Glycan Synthesis is Catalyzed by Enzymes of Glycosylation – the “Glycozymes” Protein Glycosylation – Relationship Between N-linked and O-linked Glycoproteins N-linked Glycoproteins O-linked Glycoproteins O- and N-linked Glycan Chain Extension and Commonly Occurring Glycan Motifs Analytical Methodologies Developed to Detect and Characterize Glycosylation Conclusion References