The advent of bupropion hydrochloride sustained release (Zyban) has heralded a major change in the options available for smoking cessation pharmacotherapy. Bupropion is a selective re-uptake inhibitor of dopamine and noradrenalin which prevents or reduces cravings and other features of nicotine withdrawal. Bupropion is a useful oral and non-nicotine form of pharmacotherapy for smoking cessation. For this review a total of 221 papers were reviewed plus poster presentations. This review examines in detail original clinical trials on efficacy, categorised according to whether they were acute treatment trials in healthy smokers; studies in specific populations such as people with depression, chronic obstructive pulmonary disease (COPD) or cardiovascular disease; or relapse prevention studies. Overall, these studies in varying populations comprising over four thousand subjects, showed bupropion consistently produces a positive effect on smoking cessation outcomes. The evidence highlights the major public health role that bupropion has in smoking cessation. The methodological issues of published clinical trials reporting one year outcomes were examined in detail including: completeness of follow-up; loss to follow-up; intention to treat analysis; blindness of assessment; and validation of smoking status. The review discusses contraindications, adverse effects, dose and overdose, addictive potential, and the role of bupropion in reducing cessation-related weight gain. Bupropion combined with or compared to other pharmacotherapies (nicotine patch; nortriptyline) is considered. Impressive evidence exists for the use of bupropion in smoking cessation among difficult patients who are hard-core smokers such as those with cardiovascular disease, chronic obstructive pulmonary disease (COPD) and depression. Bupropion reduces withdrawal symptoms as well as weight gain and is effective for smoking cessation for people with and without a history of depression or alcoholism. Serious side effects of bupropion use are rare. The major safety issue with bupropion is risk of seizures (estimated at approximately 0.1%) and it should not be prescribed to patients with a current seizure disorder or any history of seizures. In clinical trials of bupropion for smoking cessation no seizures were reported. Allergic reactions occur at a rate of approximately 3% and minor adverse effects are common including dry mouth and insomnia.