A variety of evidence suggests important commonalities in the neurochemical basis of reinforcement in pathological gambling (PG) and psychostimulant addiction. This article focuses on the parallel and specific roles that dopamine (DA) activation plays in these two disorders, beyond its generic role in reinforcement. A psychostimulant-mimetic model for PG is proposed based on evidence from the following domains: Acute subjective-behavioral effects of gambling and psychostimulants; Effects of anticipated rewards and uncertainty of reward delivery (key elements of gambling) on DA release; Relationship between DA release and positive arousal; Cross-priming of motivation for gambling by amphetamine; Effects of DA D2 antagonists on gambling and amphetamine reward; Effects of mixed D1-D2 antagonists on clinical symptoms of PG; Effects of DA D2 agonists on experimental measures of risk-taking, gambling, and induction of PG in patients with Parkinson's disease; Electrophysiological and cognitive disturbances associated with chronic exposure to gambling and psychostimulants, and the possible role of sensitization in these effects. Limitations of the model regarding the exclusive role of DA are discussed with particular reference to genetic risk, co-morbidity, and sub-types of PG. Suggestions for future research include isolating the roles of DA receptor subtypes in PG, and parallel within-subject assessment of DA manipulations on gambling and psychostimulant reinforcement in PG subjects and controls.