The "Supplementation en VItamines et Minéraux AntioXydants" (SU.VI.MAX) Study is a randomized double-blind, placebo-controlled, primary-prevention trial designed to test the efficacy of a daily supplementation with antioxidant vitamins and minerals, in reducing cancer and ischaemic vascular disease incidence in a general population. 14,412 subjects living in France (women aged 35 to 60, and men 45 to 60) were selected from 79,976 volunteers enrolled after a five-month (March-July 1994) national multimedia campaign. Of these subjects 13,017 were assigned at random to one of two groups. Immediately after randomisation, 270 subjects declared that they were no longer willing participate in the study and 6 subjects were recognised as ineligible (out of the age range after verification). Supplementation consisted to a combination of 120 mg vitamin C, 30 mg vitamin E, 6 mg beta-carotene, 100 µg selenium (as selenium-enriched yeast) and 20 mg zinc (as gluconate); or a matching placebo in a single daily capsule. At enrolment and at 12-18 months intervals, participants were invited to visit a mobile medical unit or a preventive health center. Subjects were asked to complete a monthly questionnaire, summarising treatment compliance and health events, via Minitel (a phone-based French terminal), the internet or mail. Primary outcomes were major ischaemic events (ICD codes 120-124) and cancer of any kind, except for basal cell carcinoma of the skin. Secondary outcome was all-cause mortality. After a median follow-up time of 7.5 years, intention-to-treat comparisons were performed between both groups.