The purpose of this study is to examine how Buprenorphine, a form of opioid addiction treatment, changes the ability to think and reason among people addicted to opiates, who are either HIV negative or HIV positive. In addition, blood samples will be stored for HIV+ and HIV- individuals who take buprenorphine to study its effect. We hypothesize that the HIV positive participants will demonstrate significant improvement in thinking and reasoning ability at 3 and 6 months compared to baseline, but that their thinking and reasoning ability will still be lower than HIV negative participants. We also hypothesize that the biomarkers in participants' blood samples will be associated with measures of change in thinking and reasoning ability.