Background: My long-term goal is to become an independent VA health services researcher focused on designing and testing integrated care solutions to improve mental health and substance abuse (MHSA) services access, quality, and outcomes for vulnerable Veteran populations. This CDA-2 will provide me with the necessary mentorship, skills, and experiences to evaluate, modify and implement organizational changes that improve MHSA outcomes for vulnerable Veterans in primary care settings. Significance/Impact: Veterans who have been homeless have high rates of depression and opioid use disorder and barriers to accessing traditional primary care services. It is important to determine effective models of MHSA services integration at this time when Veterans have more options for care in VA and community settings. VA’s homeless patient aligned care team (H-PACT) program, implemented in over 60 VA facilities, offers a natural laboratory to determine optimal approaches of MHSA services integration to advance Veteran health. My research will impact Veteran health by determining the effectiveness of H-PACT for providing high quality MHSA care and mitigating adverse MHSA outcomes among homeless-experienced Veterans; and by determining the unique and potentially modifiable aspects of H-PACT and other patient aligned care teams (PACTs) that could be scaled to achieve superior MHSA outcomes for homeless-experienced Veterans in specialized and non-specialized PACT settings. This research strongly aligns with VA research priorities of mental health and primary care, and legislative priorities related to addiction recovery and community care. Innovation: While prior studies suggest H-PACT improves primary care utilization and Veteran experiences with care, there is less research focused on determining what features of H-PACT are successful. We lack data on clinical process measures and outcomes for Veterans empaneled in H-PACTs, information on aspects of MHSA services integration that exists within H-PACTs and traditional PACTs caring for homeless-experienced Veterans, and the barriers and facilitators that contribute to MHSA quality for homeless-experienced Veterans. Specific Aims: My CDA-2 has three primary aims: 1) Compare MHSA services quality of care (e.g., clinical performance measures for depression, opioid use disorder) and outcomes (e.g., psychiatric hospitalization, opioid-related overdose, suicide) for homeless-experienced Veterans empaneled in H-PACTs versus other PACTs in the same facilities; 2) Measure levels and features of MHSA services integration (e.g., coordination with community services, co-location of providers, full integration) for homeless-experienced Veterans in H- PACTs and other PACTs; and 3) Evaluate MHSA service practices and barriers in 4 facilities ranked low and 4 ranked high on measures of MHSA services quality for homeless-experienced Veterans. I will work with my mentors to develop the expertise to study MHSA services quality i...