The "SUpplementation en VItamines et Minéraux AntioXydants" (SU.VI.MAX) Study is a randomized double-blind, placebo-controlled, primary-prevention trial which started in 1994 in France. This epidemiologic study is designed to test the efficacy of a daily supplementation with antioxidant vitamins (vitamin C, 120 mg, vitamin E, 30 mg, and beta-carotene, 6 mg) and minerals (selenium, 100 microg, and zinc, 20 mg) at nutritional doses, in reducing the main causes of premature death (cancers and cardiovascular diseases); 12,735 eligible subjects (women aged 35 to 60 years, and men aged 45 to 60 years) were included in 1994 and and will be followed up for 8 years. Participants undergo a yearly visit consisting, every other year, of either biological sampling or clinical examination. They also regularly provide information on health events and dietary intake by filling out computerized questionnaires using the Minitel Telematic Network. After 2 years of supplementation, biochemical indicators of vitamin and trace element status reach reasonable level without reaching concentrations as high as those observed in intervention studies, which tested relatively high doses of antioxidants, and ended up with higher risk of pathology.