The present paper provides an overview of dopamine (DA) and cholecystokinin (CCK) mechanisms that contribute to psychostimulant reward-related behaviors. Three different behavioral paradigms are focused on: intravenous psychostimulant reward, psychostimulant-induced locomotor activity, and psychostimulant-induced feeding. Based on evidence derived from these different behavioral paradigms, this paper reviews data indicating that nucleus accumbens CCK and DA play an important role in mediating reward. Neurobiological mechanisms are proposed to explain the functional relationship between CCK and DA in the nucleus accumbens.