This is a randomized controlled trial of injectable intramuscular naltrexone (XR-NTX) versus intramuscular placebo among HIV-infected prisoners meeting Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) criteria for alcohol dependence or problem drinking, who are transitioning to the community and seeking treatment to prevent relapse to alcohol use. We hypothesize that extended release naltrexone (XR-NTX) will result in improved HIV outcomes (lower log10 HIV-1RNA levels and higher CD4 count) as well as improved alcohol treatment outcomes, and reduced drug/sex HIV related risk behaviors and decreased rates of reincarceration.