Although glycoproteins and proteoglycans have been a subject of re­ search for many years, it is only during the last five or so years that they have aroused the interest of a very broad cross section of investigators in the biological sciences. The reason for this expanded interest in these molecules is simple: not only are glycoproteins and proteoglycans ubiq­ uitous, but many are molecules with well-defined and important biological functions. The list of molecules that fall into this category grows daily; interferon, immunoglobulins, certain hormones, many cell surface recep­ tors, and viral coat proteins are but a few examples. Thus, investigators with interests as diverse as viral replication. cell-cell interactions. poly­ isoprenoid synthesis, secretory processes, hormone responses, embryonic development, and immunology have become concerned with glycopro­ teins and proteoglycans. The objective of this book is to summarize the current state of knowledge on the biochemistry of these molecules. Coverage is by no means encyclopedic; rather the thrust is to emphasize the recent ad­ vances. The first chapter deals primarily with structural work on the oligosaccharide chains of glycoproteins, but it will be apparent in it and in the succeeding two chapters on biosynthesis that not only do structural studies aid biosynthetic investigations, but that studies on biosynthesis often playa major role in elucidation of structure.