Modern trait theories of personality include a dimension reflecting positive emotionality (PE) based on sensitivity to signals of incentive-reward. In animals, responsivity within an emotional system analog of PE is dependent on brain dopamine (DA) activity. To determine whether human PE trait levels are also associated with central DA, effects of a specific DA D2 receptor agonist were assessed in Ss who were widely distributed along the trait dimension of PE. The degree of agonist-induced reactivity in two distinct central DA indices was strongly and specifically associated with trait levels of PE, but not with other personality traits. The results suggest that the trait structure of personality may be related to individual differences in brain DA functioning.