Bupropion was initially developed and licensed for the treatment of major depressive disorder in the United States in 1989. It was licensed as a pharmacotherapy for smoking cessation in the United States in 1997 and in the United Kingdom in 2000, and for the prevention of seasonal major depressive episodes in patients with seasonal affective disorder in the United States in 2006. Its main mechanism of action is believed to be via dopamine and noradrenalin reuptake inhibition. In addition to proven clinical efficacy for the treatment of major depression, the prevention of depressive episodes in patients with seasonal affective disorder, and as an aid to smoking cessation treatment, bupropion has demonstrated efficacy for attenuation of symptoms of attention deficit hyperactivity disorder, and more recently it has shown anti-inflammatory action against proinflammatory cytokines such as tumor necrosis factor-alpha (TNF-alpha), which may be implicated in a number of inflammatory diseases such as Crohn's disease. The twice-daily sustained-release formulation has been extensively evaluated for smoking cessation and has shown continuous smoking abstinence rates at one year of the order of 20% across many clinical groups including healthy smokers, and smokers with cardiovascular disease, chronic obstructive airways disease, depression and schizophrenia. Bupropion is well tolerated with side effects including insomnia, headache, dry mouth, dizziness and nausea. Bupropion is a cytochrome p450 2D6 inhibitor and care must be taken when coprescribing with drugs cleared by this enzyme and when coprescribing with drugs that lower seizure threshold. Despite the clinical effectiveness and cost-effectiveness of bupropion as an aid to smoking cessation, its uptake for this indication remains low when compared with nicotine replacement therapy.