AbstractBoth the provitaminβ‐carotene and natural vitamin A and its derivatives (the retinoids) are being proposed as potential chemopreventive agents. The biochemistry and pharmacology of vitamin A suggest a number of mechanisms whereby carcinogenesis can be affected. Epidemiologic studies have consistently demonstrated an increased relative risk of cancer for people with low vitamin A intake or low‐to‐normal serum retinol values. Chemoprevention trials in humans are only now beginning. In the interim, daily consumption of vitamin‐A‐containing foods may be a‘'prescription'’worth folio wing.