As the prevalence of tobacco use has decreased, it has become clear that individuals with mental illness comprise a substantial portion of the remaining smokers. Seventy to eighty percent of patients with schizophrenia smoke and their smoking is established before their first psychotic episodes or the initiation of treatment. Many patients with schizophrenia, and approximately 50% of their first degree relatives have abnormalities in auditory sensory gating and / or smooth pursuit eye movements. These abnormalities are corrected by nicotine, and they appear to be transmitted as autosomal dominant traits. Evidence is accumulating that these abnormalities reflect genetic variations in nicotine receptor number and function, that may increase susceptibility for schizophrenia. Recent studies suggest that bupropion, added to treatment with an atypical antipsychotic, can enhance the likelihood of smoking cessation or reduction in patients with schizophrenia. The prevalence of smoking is also substantially increased among patients with bipolar disorder, perhaps especially so among those with psychotic features. Nicotine delivered by gum or transdermal patch can provide short term relief for exacerbations of Tourettes Syndrome, but its use is limited by frequent toxicity, primarily nausea.