Résumé : The carbohydrate diet providing 1576 ± 281 kcalories under the form of glucides per day for 8 days induces a limited reduction of body weight. It does not alter the blood sugar level (only the sample of the 4th day was taken 45 min after a meal) and a normal insulin response occurs. Surprisingly the diet is not followed by any marked change in VLDL protein and lipid concentrations except for the last sample. A slight progressive decrease of HDL proteins and of total plasma-, HDL- and LDL-cholesterol and phospholipid are shown. Prealbumin values follow precisely the changes in HDL cholesterol. HDL apoprotein patterns are normal for all samples. Fraction V representing 4.6% of total apo HDL on the first and 2nd days increases slightly to 5.1 and 5.7% on the 6th and 8th days, respectively. Amounts in Fraction III (apo A-1 = 55.0% of total apoproteins) and in Fraction IV (apo A-II = 20.0%) and consequently the apo A-1/A-II ratio, remain stable during the whole experiment. The relative percentage of the different apoproteins show a progressive increase of apoproteins S4, S5 and S6 and a visible simultaneous decrease of apo C-II, C-III and apo D-2. The absolute amounts of apo S increase from less than 0.5 mg/dl to 1.6 mg/dl of plasma.