Premalignant lesions: role of antioxidant vitamins and beta-carotene in risk reduction and prevention of malignant transformation. Epidemiological studies have shown that diets rich in one or more antioxidant nutrients may reduce the risk of cancers of the lung, uterine cervix, mouth, and gastrointestinal tract. Study of premalignant lesions offers a comparatively expedient approach to identifying and evaluating the efficacy of the cancer chemopreventive components of foods. Some recent findings suggest roles for beta-carotene and/or vitamin C in reversing or reducing the risk of cervical dysplasia and oral leukoplakia. There are some indications that vitamin C and beta-carotene may reduce the risk of atrophic gastritis and gastric cancer. Additional epidemiological and molecular biology studies and clinical intervention trials using premalignant lesions as the marker of specific cancer risks should become an important component of future research in the area of cancer chemoprevention. 