Cholesterol is an indispensible structural building block for cell membranes, responsible for membrane fluidity and permeability, intracellular transport, signal transduction and cell trafficking. It is a white and waxy substance, an essential type of fat called lipoproteins carried in the blood stream of particles. Cholesterol plays an essential role in the maintenance of the integrity of biologic membranes and serves as a precursor in the synthesis of many endocrine mediators. It is also synthesized in mammalian cells via the mevalonate pathway. It has demonstrated a possible linkage of cholesterol to some diseases, such as prostatic cancer, benign prostatic hyperplasia, coronary heart disease, and cerebral thrombosis. Cholesterol has many biological functions. Depending on the cell types, the cholesterol content of cell membranes varies. The membranes of most cells have an intermediate cholesterol/phospholipid ratio and possess both protective and metabolite-transport functions.