Studies demonstrate that methamphetamine (meth) use is associated with high-risk sexual behavior among men who have sex with men (MSM), putting meth-using MSM at extraordinarily high risk for transmitting or acquiring HIV. This study is a randomized, double-blind, placebo-controlled trial of the medication aripiprazole for methamphetamine-using individuals, including MSM, and will assess efficacy, acceptability, tolerability, safety, and adherence to study medication.