Some cholesterol is present in cell membranes as a component of lipid rafts. Lipid rafts have been implicated in a range of physiological processes.

Circulating cholesterol is found in lipoprotein complexes, notably HDL and LDL. There is good evidence that relatively high levels of HDL are protective against cardiovascular disease because it is responsible for reverse cholesterol transport.

There is also good evidence that relatively high levels of LDL are a risk factor for cardiovascular disease, specially when LDL becomes oxidised.