During the past few years considerable progress has been made in each of these areas. In addition, much new information has accumulated on the occurrence of oligosaccharide processing in the animal and plant kingdoms and on the repertoire of asparagine-linked oligosaccharides that are synthesized in nature. In this review we have attempted to focus on this new information, particularly the factors that serve to control the extent of processing and thereby determine the final oligosaccharide structures that are assembled. We will begin with a brief review of asparagine-linked oligosaccharide structure, including examples of recently deduced structures. Due to space limitations we are not able to review the important advances that have been made in the area of oligosaccharide structural analysis and the determination of oligosaccharide conformation. The interested reader is referred to several recent reviews of these topics (2-5). In addition, the reader may wish to consult other recent reviews on the synthesis of asparagine-linked oligosaccharides (6-9a).