These studies are directed toward the elucidation of the molecular structure of plasma lipoproteins, and the role that primary structure plays in lipid-protein and protein-protein interactions. In addition, the role of plasma lipoproteins as cofactors for enzymes, precursors for steroidogenesis, vehicles for lipid transport, and regulators of cholesterol biosynthesis are systematically being investigated. A detailed knowledge of the chemistry of the plasma lipoproteins is a prerequisite to our understanding of lipid transport in normal and dyslipoproteinemic subjects.