Glycobiology is the study of the structure, biosynthesis and biology of saccharides that are widely distributed in nature and are essential components of all living things. This field combines expertise in both carbohydrate biochemistry and molecular biology. The ABC drug transporter, P glycoprotein or MDR1 is one such example discussed in this book. The relationship of glycosphingolipid (GSL) biosynthesis to the Pgp-mediated multiple drug resistance phenotype, and the role of MDR1 in lipid biosynthesis in particular is evaluated. The structure and activities of natural complex polysaccharides are also analysed. Specifically, heparin (Hep) as an anticoagulant and antithrombotic (macro)molecule and CS in the treatment of osteoarthritis is reviewed, and the GAG structure-function relationship, which has led to the discovery of novel drugs for the possible treatment of some serious diseases. The gene targeting analyses of certain enzymes, which revealed that the HNK-1 carbohydrate plays important roles in synaptic plasticity and memory function, is described as well. Recent work on the topic protein-specific glycosylation is highlighted also, focusing on the primary structure of a protein which directly exerts a cis-control of the glycosylation event.