During the period of a low vitamin C intake (approximately equal to 20 mg per day) ascorbic acid in a dose of 2 x 500 mg per day was administered to 82 men and women aged 50-75 years. A correlation of plasma cholesterol levels determined before and after a three months' administration of ascorbic acid showed the effect of vitamin C to be dependent on the starting concentration of plasma cholesterol: the higher the initial cholesterolemia, the greater the hypocholesterolemic effect of ascorbic acid. On restricting the experimental group to subjects with an initial cholesterolemia above 230 mg%, the effect of the same dose of ascorbic acid on cholesterolemia was followed in three-month periods for a further 9 months. In all these time intervals, ascorbic acid was found significantly to depress cholesterolemia and its effects persisted 6 weeks after termination of the experiment. The administration of 2 x 500 mg ascorbic acid daily during one year resulted in an abrupt increase of ascorbemia and a marked accumulation of ascorbic acid in the leucocytes. Six weeks following interruption of ascorbic acid intake, vitamin C concentration in the leucocytes significantly declined but still continued to be twice higher than in the control receiving no ascorbic acid supplement.