The Recommended Dietary Allowance of vitamin C (ascorbic acid) for adults has now been set at 45 mg day(-1) by the U.S. Food and Nutrition Board. This intake suffices to prevent scurvy in most people. It is, however, much less than the optimum intake, the intake that leads to the best of health. A larger intake decreases the incidence and severity of the common cold and other diseases. Ascorbic acid has antiviral and antibacterial activity and is required for phagocytic activity of leukocytes. Several arguments indicate that for different human beings the optimum intake lies between 250 mg day(-1) and a much higher value, 5000 mg day(-1) or more. It is proposed that the present Recommended Dietary Allowance of 45 mg day(-1) of vitamin C for adults be renamed the Minimum Dietary Allowance, defined as the amount needed to prevent scurvy, and that, after consideration of the evidence about intake and the best of health, there be formulated another category of values, the Recommended Daily Intake, with the suggested range of 250 mg day(-1) to 4000 mg day(-1) of ascorbic acid for an adult.