Triglyceride-rich lipoproteins are secreted by hepatocytes and intestinal enterocytes for the transport of triglycerides (TAG) between tissues. Lipoproteins are lipid emulsion particles with a neutral lipid core, surrounded by a phospholipid monolayer with associated apolipoproteins. Apolipoprotein B (apoB) is the structural protein of TAG-rich lipoproteins and remains with low-density lipoprotein (LDL) in the circulation. Cholesterol within the particles can be used by the cell to make membranes, but if LDL accumulates in the circulation there is increased risk for the development of vascular disease, with accumulation of the cholesterol in the blood vessel wall. Assembly and secretion of TAG-rich lipoproteins depend on apoB, lipids and transport proteins for the movement of TAG between cellular compartments. Regulation of the assembly and secretion of the TAG-rich lipoproteins occurs at multiple levels, including the degradation of the apoB protein or the intact lipoprotein particle.