The ATBC Study, a project between Finland's National Public Health Institute (NPHI) and NCI, was conducted to determine whether daily supplementation with alpha-tocopherol, beta-carotene, or both, would reduce the incidence of lung or other cancers. Male smokers between the ages of 50 and 69 were recruited from southwestern Finland between April 1985 and June 1988. A total of 29,133 men were randomly assigned to one of four intervention groups: 50 mg/day alpha-tocopherol (as dl-alpha-tocopheryl acetate); 20 mg/day beta-carotene; both alpha-tocopherol and beta-carotene; or placebo. They were followed for five to eight years during the trial, until death, or 30 April 1993 when intervention was stopped (median follow-up, 6.1 years). Follow-up for endpoints was continued postintervention.