The nucleus accumbens is part of the neural circuit that controls reward-seeking in response to reward-predictive cues. Dopamine release in the accumbens is essential for the normal functioning of this circuit. Previous studies have shown that injection of dopamine receptor antagonists into the accumbens severely impairs an animal's ability to perform operant behaviors specified by predictive cues. Furthermore, excitations and inhibitions of accumbens neurons evoked by such cues are abolished by inactivation of the ventral tegmental area, the major dopaminergic input to the accumbens. These results indicate that dopamine is necessary to elicit neural activity in the accumbens that drives the behavioral response to cues. Here we show that accumbens dopamine release is causal to the rats' reward-seeking behavioral response by demonstrating that dopamine in this structure is both necessary and sufficient to promote the appropriate behavioral response to reward-predictive cues.