Project Abstract This dissertation aims to better understand what substance use, treatment, and mental health outcomes occur after men of color who have sex with men (MoCSM) who live in Los Angeles, CA exit formal substance abuse treatment (SAT) programs, and if these outcomes vary across people living with HIV (PWH) versus people living without HIV (PWOH). The objective of the research is to identify which social and structural factors impede or foster positive SAT engagement, substance use reduction, depression, and anxiety outcomes in order to promote a higher quality of life for MoCSM in recovery. These goals will be met using data from the NIDA-funded mSTUDY (U01 DA036267) prospective cohort of over 500 MoCSM in Los Angeles, approximately half of whom are PWH, and will be accomplished through the following aims: Aim 1: Using longitudinal data from a cohort of MoCSM (2014-2023), describe engagement in, exits, and re-entry into SAT. Assess how sociodemographic factors, baseline substance use, and HIV status are associated with SAT at baseline and during follow up. Aim 2: Evaluate changes in self-reported frequency of methamphetamine, cocaine, cannabis, tobacco, and alcohol use among mSTUDY participants who have exited substance abuse treatment up to 3 years post-treatment. Among people use methamphetamine, cocaine, cannabis, tobacco, or alcohol at baseline, assess if people with prior SAT use those substances at a lower frequency than people who have never been in treatment, and if use outcomes vary by HIV status. Aim 3: Assess if there are differences in depression or anxiety symptoms (respectively measured by CES-D 13 and GAD-7 14) following SAT among people with and without prior SAT. Evaluate if these associations vary by HIV status. Among people in recovery, assess if higher social support scores (measured by MSPSS 15) are associated with improved depression and anxiety outcomes. Outcomes will be assessed across 4,319 study visits conducted across 129 men with prior SAT at baseline, 91 men who first entered SAT during follow-up, and 358 men who use substances but have never received treatment. Descriptive statistics and data visualization will be performed, and these outcomes will be assessed through multinomial regression, logistic regression, and generalized estimating equations, as appropriate, adjusting for relevant confounding factors. Through assessing the understudied, longer-term mental health, treatment, and substance abuse factors following substance abuse treatment, and analyzing the differences in these outcomes due to structural factors, this dissertation will help understand what supports better recovery outcomes among community-based MoCSM living with and without HIV in Los Angeles.