Helping cigarette smokers to permanently stop smoking is one of the most effective ways to prevent cancer. A physician's instruction to a patient to stop smoking and to offer assistance in this endeavor is an important motivator. Current guidelines state that clinicians should encourage all smokers who want to quit to use medications and should offer psychosocial therapies, as well. It has been shown that even brief clinician advice about smoking cessation increases quit rates. Five medications--bupropion, nicotine gum, nicotine inhaler, nicotine nasal spray, and nicotine patch--and one proven psychosocial therapy (behavior therapy) appear equally effective and safe; i.e., they all double quit rates and are associated with a less than 5% dropout rate due to adverse events. In 1998, approximately one third of those who attempted to quit smoking used a medication. Attending group behavior therapy to supplement medications increases quit rates but is not essential for medications to work. As there are no proven treatment-matching protocols, patients should choose the treatment(s) they believe will be most effective for them. In the future, people who continue to smoke will be individuals with severe nicotine dependence or psychiatric symptoms; thus, clinicians will increasingly be called on to provide pharmacotherapy for smoking cessation.