Cigarette smoking, and by implication nicotine, may be involved as a negative or positive risk factor in some neuropsychiatric disorders and possibly as a treatment in others. Nicotine exposure may be a negative risk factor for the development of Parkinson's disease, but a positive risk factor for the development of tardive dyskinesia. For Alzheimer's disease and Tourette's syndrome, the role of nicotine exposure is equivocal, however, the role of nicotine as a possible therapeutic agent, alone or in combination, remains an intriguing question. For functional psychiatric disorders, the data are suggestive of a link between tobacco use and at least exacerbation of some disorders. While nicotine exposure is unlikely to be critical in the genesis of these disorders, it may complicate the pharmacological therapeutics and long-term prognosis. Further research is needed to examine the actual importance of tobacco use in behavioural disturbances. The relative importance of central nicotinic mechanisms in normal and disordered human cognition and movement is now beginning to be fully explored.