Glycoconjugates such as glycoproteins and glycolipids play important roles in cell-cell interaction events, including development, differentiation, m- phogenesis, fertilization, inflammation, and metastasis. A number of reports have documented the association of unique oligosaccharide sequences to p- tein targeting and folding, and in mechanisms of infection, inflammation, and immunity. For glycoproteins, these glycan appendages are the result of extensive co- or post-translational modifications of the nascent proteins in the endoplasmic reticulum and in the Golgi apparatus. Although nucleic acids and proteins are copied from a template in a repeated series of identical steps using the same enzymes, complex carbohydrates are formed by the sequential actions of cellular glycosyltransferases that specifically recognize unique s- strates. The molecular biology of these transferases and other carbohydra- modifying enzymes is providing important insights on oligosaccharide recognition events. While it is acknowledged that the definition of the protein complement of cells and tissues (the so-called proteome) remains an enormous task in this postgenomic era, the characterization of all glycans produced by individual organisms (referred to as the glycome) presents an equally imp- tant challenge. This task is further complicated by the fact that oligosacc- rides cannot presently be cloned. These complex carbohydrates exist in a staggering diversity of structures, linkages, and branching, thus providing an exquisite molecular repertoire for cellular interactions.