 The lack of success in treating substance abuse may be contributed to by a limited understanding of the clinical neurobiology of drug abuse. A better understanding of such deficits might aid in the development of more relevant pharmacological and psychosocial treatment approaches. Thus, the purpose of this study is to test the hypothesis that repetitive illicit drug use may be associated with cortical and subcortical structural abnormalities, vascular abnormalities, as well as neuropsychological decrements. Additionally, a battery of psychological tests are administered to provide information about demographics, drug use, neurocognitive measures, and personality structures. 