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A majority of habitual tobacco smokers find it very difficult to quit the habit because they become addicted to the nicotine present in tobacco smoke. Nicotine, like other psychostimulant drugs of abuse, increases dopamine release in the principal terminal field of the mesolimbic system, the nucleus accumbens, and there is evidence that this mediates the ‘rewarding’ properties of the drug, which reinforce its self-administration. This review focuses on the working hypothesis that addiction to nicotine, and other psychostimulant drugs, depends upon their ability to evoke a sustained increase in dopamine release directly into the extracellular space which lies between the cells in the nucleus accumbens where it stimulates extra-synaptic dopamine receptors. It is suggested that increased stimulation of these receptors is associated with increased incentive learning or the attribution of increased incentive salience to the …