The dietary supplement Avmacol contains precursors of sulforaphane, a broccoli extract that is an inducer of carcinogen metabolism. The proposed clinical trial shall address whether treatment with Avmacol, either 4 or 8 tablets per day, results in enhanced detoxification of tobacco-related carcinogens in healthy current smokers. The ultimate goal is to determine if this supplement can be used for prevention of tobacco-related malignancies, such as head and neck or lung cancer.