Supplemental use of vitamins to prevent disease constitutes a major commercial enterprise in the United States. The efficacy of such use, or even the need for intakes above that which can be supplied by means of diet alone, has been the source of considerable controversy in the medical and scientific fields. Recently published data have given strong support to several of the claims for major benefits of disease prevention, including that of cancer, cardiovascular disease, carpal tunnel syndrome, and neural tube defects, to name just a few. The purported benefits for supplemental vitamin usage are discussed for these diseases, along with a call for a re-evaluation of the underlying philosophy of the Recommended Dietary Allowances, or consideration of their abolition, based on newly emerging data.