Despite the reality that smoking remains the most important preventable cause of death and disability, most clinicians underperform in helping smokers quit. Of the 46 million current smokers in the United States, 70% say they would like to quit, but only a small fraction are able to do so on their own because nicotine is so highly addictive. One third to one half of all smokers die prematurely. Reasons clinicians avoid helping smokers quit include time constraints, lack of expertise, lack of financial incentives, respect for a smoker's privacy, fear that a negative message might lose customers, pessimism because most smokers are unable to quit, stigma, and clinicians being smokers. The gold standard for cessation treatment is the 5 As (ask, advise, assess, assist, and arrange). Yet, only a minority of physicians know about these, and fewer put them to use. Acceptable shortcuts are asking, advising, and referring to a telephone "quit line" or an internal referral system. Successful treatment combines counseling with pharmacotherapy (nicotine replacement therapy with or without psychotropic medication such as bupropion). Nicotine replacement therapy comes in long-acting (patch) or short-acting (gum, lozenge, nasal spray, or inhaler) forms. Ways to counter clinicians' pessimism about cessation include the knowledge that most smokers require multiple quit attempts before they succeed, that rigorous studies show long-term quit rates of 14% to 20%, with 1 report as high as 35%, that cessation rates for users of telephone quit lines and integrated health care systems are comparable with those of individual clinicians, and that no other clinical intervention can offer such a large potential benefit.