Results from a pilot study to assess the feasibility of conducting a full-scale lung-cancer-prevention trial using pharmacologic beta-carotene are reported. Participants in the study were randomized in a double-blind fashion to receive either 15 mg orally of beta-carotene or placebo daily. Findings for the first 300 men to complete 1 y on study are presented. After 10 mo of treatment, serum levels in the placebo group showed essentially no change whereas levels in the treated group increased almost 10-fold after 4 mo of treatment. The relationship between change in serum levels are evaluated in regard to body mass index, alcohol consumption, amount of smoking, lipids, and other variables. The results to date clearly indicate that substantial serum response can be achieved with only 15 mg/d and that with this dosage no skin discoloration or other toxicities are observed.