Diet is fundamental in the treatment of primary hyperlipoproteinaemias. The author outlines nutritional factors affecting serum lipoproteins. In the treatment of hypercholesterolaemia the most effective is the reduction of the intake of saturated fatty acids, it being twice as effective as the reduction of dietary cholesterol, which is necessary as well. The proportion of the saturated, poly- and monounsaturated fatty acids is recommended to be 10-10-10 percent of the overall calorie intake. Such a composition of diet has no disadvantageous effect on the level of HDL cholesterol. Of carbohydrates the consumption of sugar and alcohol should be limited in the presence of hypertriglyceridaemia and/or obesity. Water soluble dietary fibres may have a cholesterol-lowering effect. The reduction of overall calorie intake is indispensable in hyperlipoproteinaemias with obesity. As a result of the diet a 10-20 percent decrease in the level of cholesterol and--in some cases--the normalization of hypertriglyceridaemia can be expected.