There is increasing evidence that the sympathetic-adrenal medullary (SAM) system mediates some of the physiological, behavioral and subjective effects of cocaine and nicotine and plays an important role in the abuse potential of these psychostimulants in humans. The primary goals of the proposed systematic set of studies are to determine the role of SAM in the reinforcing effects of cocaine and nicotine, and to determine whether adrenergic blockers may be a potential medication for cocaine abuse and nicotine dependence.