Effective treatment of nicotine addiction is essential for reducing the substantial current and predicted morbidity and mortality associated with tobacco smoking. Despite the availability of effective treatments for smoking cessation, such as nicotine replacement therapy and bupropion sustained-release (SR), abstinence rates remain less than optimal. Varenicline is the first in a new class of agents for smoking cessation, the alpha(4)beta(2) nicotinic acetylcholine receptor (nAChR) partial agonists. Nicotine addiction is mediated by stimulation of central alpha(4)beta(2) nAChRs by nicotine, which causes the release of dopamine, ultimately leading to the pleasurable effects of smoking. As a nAChR partial agonist, varenicline attenuates the craving and withdrawal symptoms that occur with abstinence from nicotine and also reduces the rewarding effects of nicotine obtained from smoking in patients who lapse. Thus, varenicline offers a new therapeutic option for the treatment of nicotine addiction. Clinical trials have demonstrated superior efficacy of this agent over placebo and bupropion-SR for achieving abstinence from smoking, and varenicline has also been shown to significantly delay smoking relapse. As the newest agent approved for smoking cessation, the mechanism of action, efficacy, and safety of varenicline.