 The overall objective of this study is to determine the effect that cocaine administration has upon the experience of reward in dependent individuals and the contribution of reward processing or dysfunction to the reinforcing effects of cocaine and the recidivism rates noted in cocaine-dependent individuals. The primary goal is to employ functional magnetic resonance imaging fMRI to ascertain the function of neural systems that respond to cocaine in human participants and to determine the role that they play in the processing of different types of rewarding stimuli during episodes where individuals are drug-free and those where they are under the acute influence of cocaine. 