Since membrane glycoproteins have been implicated in many neurobiological processes and functions (see Chapters 7, 8, and 11), the mechanisms and regulation of biosynthesis of the oligosaccharide units have been of great interest to cell and neurobiologists during the past 20 years. Much of this research activity has focused on the structure, biosynthesis, and function of N-linked oligosaccharides because the majority of the carbohydrate chains attached to membrane glycoproteins in nervous tissue are attached via N-glycosidic bonds (Krusius and Finne, 1977). For further discussion of the structural details of carbohydrate units of brain glycoproteins, see Chapter 3.