Postprandial lipoprotein metabolism has been evaluated by measuring triglyceride concentrations in whole plasma and in lipoprotein fractions after an oral fat load. This approach has yielded important insights into the relation of triglyceride metabolism to lipoprotein lipase, to other lipoproteins, particularly HDL, and, most importantly, to coronary heart disease. Biosynthetic labelling of intestinal lipoproteins with vitamin A esters allows tracing of the non-degradable cholesteryl ester portion of chylomicrons and their remnants. A limitation of the method is that vitamin A is subject to neutral lipid transfer. Quantification of apolipoprotein B48, the structural protein of chylomicrons, has the potential of directly following the metabolic fate of chylomicron particles in plasma.