The mesocorticolimbic dopamine (DA) system innervates the region of the nucleus accumbens in the anterior part of the basal forebrain and appears to play a critical role in mediating not only the acute reinforcing effects of the drugs but also the motivational aspects of drug withdrawal. This chapter explains the role of mesocorticolimbic DA in the reinforcing and dependence-inducing properties of psychomotor stimulants such as cocaine and amphetamine and by extrapolation, the role of DA in more general reward processes independent of drug action. It proposes the hypothesis that the neurobiological substrates for the reinforcing actions of these drugs may involve specific parts of the basal forebrain that go beyond the nucleus accumbens to components of the “extended amygdala” including the central nucleus of the amygdala and the sublenticular part of the extended amygdala. Pharmacological treatments that increased the rate of responding for intracranial self-stimulation were hypothesized to reflect a reward enhancement.