The main objective of the Lipid and Lipoprotein Laboratory, headed by Petar Alaupovic, Ph.D., is to study the chemical, metabolic and pathiophysiologic properties of human plasma lipoproteins. These studies are based on the concept that protein components (apolipoproteins) play the essential role in the structural integrity and functional specificity of plasma lipoproteins. Two classes of lipoproteins serve as the main protein components: one characterized by apolipoprotein (apo) B and the other by apoA. There are five apolipoprotein-defined subclasses of atherogenic apoB-containing and three subclasses of antiatherogenic apoA-containing lipoproteins. One of the most clinically relevant recent findings has been that one of the apoB-containing lipoprotein subclasses with apoB and apoC as its protein components (Lp-B:C) may have a greater atherogenic capacity than the cholesterol-rich Lp-B particles widely thought the main contributors to atherosclerotic lesions. It has also been established that individual apoB-containing lipoprotein subclasses may have different responses to dietary and pharmacologic interventions. Accordingly, this laboratory is now involved in studies to (1) develop a simple test for measuring the potentially most atherogenic Lp-B:C particles, (2) participate in clinical trials studying the relative atherogenicity of apoB-containing lipoprotein subclasses and (3) determine the effect of dietary and pharmacologic interventions on individual lipoprotein subclasses.