The effects of dietary isoflavones on plasma cholesterol are discussed in order to find new diet therapies for hypercholesterolemia, which represents a cardiovascular risk factor. Isoflavones represent a class of biological substances with beneficial action in the reduction of cholesterol, LDL cholesterol, increase of HDL cholesterol and reduction of triglycerides as well as other risk factors of atherosclerotic cardiovascular diseases. The cholesterol-reducing effects of isoflavones have been demonstrated by numerous studies that started from the finding that the Japanese, consumers of more proteins of vegetal origin, present a lower incidence of ischemic heart disease, the mortality rate by cardiovascular disease being about half of that of the U.S.A. Subsequent studies were carried out in patient groups with high, average, small, or normal cholesterol levels, adults or children, all of them reporting that a diet containing vegetal isoflavones led to the reduction of cholesterol levels.