['Brain dopamine neurons code rewarding environmental stimuli by releasing endogenous dopamine, a transmission signal that is important for reinforcement learning. Human reward-seeking gambling behavior, and especially pathological gambling, has been presumed to be modulated by brain dopamine.', 'Striatal dopamine release was studied with [(11)C]raclopride positron emission tomography (PET) during gambling with an ecologically valid slot machine gambling task. Twenty-four males with and without pathological gambling (DSM-IV) were scanned three times, and the effects of different gambling outcomes (high-reward and low-reward vs. control task) on dopamine release were evaluated.', 'Striatal dopamine was released in both groups during high-reward but also low-reward tasks. The dopamine release during the low-reward task was located in the associative part of the caudate nucleus. During the high-reward task, the effect was also seen in the ventral striatum and the magnitude of dopamine release was associated with parallel gambling "high". Furthermore, there was a positive correlation between dopamine release during the low-reward and the high-reward task. There was no general difference in the magnitude of dopamine release between pathological gamblers and controls. However, in pathological gamblers, dopamine release correlated positively with gambling symptom severity.'] Is mesolimbic dopamine release linked to symptom severity in pathological gambling?