In biological systems oligosaccharides are normally conjugated to proteins or lipids. The heterogeneity and branching of oligosaccharides allow glycoconjugates to display a further level of structural and functional diversity compared with linear proteins and nucleic acids or with lipids. This review summarizes some general principles that are emerging from the new field of glycobiology which, by addressing the molecular interactions of glycoconjugates in biological systems, spans the classical physicochemical, biological, and biochemical sciences. We discuss the genesis of glycoforms, the functional roles for glycosylation, and some general aspects of structure/function relationships with reference to N-glycosylated animal glycoproteins including the enzymes ribonuclease and tissue plasminogen activator, IgG, the family of C-type lectins, and receptor ligands.