The randomized three-group design uses repeated assessments at baseline, at the end of the 8-week intervention period, and at 3-, 6-, and 9-month post randomization follow-up. Participants in all three conditions receive brief weekly text-message assessments on their methamphetamine use and HIV sexual behaviors in the previous seven days. This study will determine the differential immediate and sustained effects of transmitting theory-based text messages by PHE (TXT-PHE) versus by automation (TXT-Auto), compared to an assessment-only (AO) control condition among out-of-treatment, methamphetamine-using MSM for reductions of methamphetamine use and HIV sexual risk behaviors. It is hypothesized that there will be significantly greater reductions in methamphetamine use and HIV sexual risk behaviors from text messages transmitted by PHE than by text messages transmitted by automation, which in turn will produce significantly greater reductions than the AO condition (PHE > TXT > AO). In addition, this study will determine the cost-effectiveness of TXT-PHE vs. TXT-Auto compared to AO for reducing methamphetamine use and HIV sexual risk behaviors. The investigators hypothesize that the TXT-PHE intervention will prove more cost-effective than TXT-Auto in reducing methamphetamine use and HIV sexual risk behaviors, while the TXT-Auto condition will prove more cost effective than the AO condition in reducing these same outcomes (PHE > TXT > AO).