 The goal of this research study is to improve the clinical care of human immunodeficiency virus HIV-infected or HIVHepatitis C HCV co-infected, alcohol-using patients by identifying significant interactions which may occur between drugs commonly used to treat HIV disease known to be cytochrome P450 CYP450 inducers or inhibitors and alcohol, the most frequently abused substance in the United States. We hypothesize that concomitant use of alcohol and currently utilized antiretroviral therapy ART will be associated with significant drug interactions including alteration of alcohol and ART pharmacokinetics as well as altered responses to alcohol administration. We plan to conduct alcohol and ART administration studies in 6 study samples n10 each: 1. those with HIVAIDS and eligible for efavirenz-containing HAART, 2. those with HIVAIDS and eligible for a ritonavir-boosted protease inhibitor based HAART, 3. those with HIVAIDS and HCV eligible for an efavirenz-containing HAART, 4. those with HIVAIDS and HCV eligible for a ritonavir-boosted protease inhibitor regimen, 5. healthy subjects taking clinically relevant doses of maraviroc and 6. those with mild HCV taking clinically relevant doses of maraviroc. Pharmacokinetics, subjective, and cognitive data will be serially collected over the course of study sessions where either alcohol or placebo is administered prior to and following ART. Data collected will elucidate the presence and clinical significance of drug interactions, both pharmacokinetic and pharmacodynamic, between alcohol and ART in these populations. 