Publisher Summary The blood and tissues of animals typically contain not only unesterified cholesterol (UC), but also cholesterol esters (CE). Most of the CE is formed from long-chain fatty acids, such as palmitic acid, oleic acid, linoleic acid, or arachidonic acid, but small amounts of cholesterol sulfate (CS) and cholesterol glucuronide also are present. This chapter provides a brief overview of the biochemistry, physiology, and pathology of these esters as an introduction to the field of CE research. It discusses the distribution and physical properties of cholesterol esters. It is clear that long-chain fatty acid esters of cholesterol are distributed very unevenly among different tissues. They are essentially absent from erythrocytes and are present in only extremely low amounts in tissues of the nervous system. On the other hand, they are present in relatively high amounts in the adrenal, ovaries and blood plasma, and the liver, too, can be relatively rich in CE. Enzymes and proteins that synthesize, transport, and hydrolyze CE are found both inside and outside of cells. In most cases, the intracellular and extracellular enzymes use entirely different cofactors and have different pH optima.