PROJECT SUMMARY/ABSTRACT More than four million U.S. residents seek treatment for substance use disorder (SUD) each year. Community reintegration following residential SUD treatment is an especially vulnerable time, withmost people who return to use following residential SUD treatment doing so in the 30 days immediately following discharge. D during information aily monitoring methods such as ecological momentary assessment (EMA) can identify higher risk periods community reintegration as well as clarify time-sensitive proximal predictors of return to use. This can help tailor the type, amount, and timing of interventions to prevent and/or delay return to use. of substance use afterEscape from and avoidance of negative affect are leading motives for re-initiation periods of abstinence. These data underscore affect dysregulation—a widely regarded transdiagnostic risk factor—as a key target for interventions to be delivered during community reintegration of SUD inpatients. Yet, knowledge/methodological/population gaps limit our understanding of affect dysregulation in SUD. (1) Virtually all research on return to use during community reintegration has used cross-sectional or traditional longitudinal designs. Pinpointing real-time proximal predictors of return to use is necessary to inform interventions that can be delivered when dysregulation and use of Studies in this area have exclusively focused on dysregulation stemming from negative affect. Positive dysregulation SUD individuals are most in need or may most benefit from them. (2) Our understanding of affect in risk for return to use i s limited. Intensive longitudina l data methods (e.g., EMA) capture within- between-person affect dynamics, which may improve detection of individuals a greatest risk for return to as well as pinpoint risk states to intervene on in momentary interventions. They also allow for examination potential clinical targets for momentary interventions, such as engagement in affect regulation strategies. 3) affec may also increase risk for return to use during community reintegration. (4) Individuals in early recovery exhibit autonomic dysfunction; thus, HRV may be an important bio-signal for detecting t ( t risk for return to use during community reintegration. (5) Community reintegration is a period of unique/intense stress for people with SUD. Research during this period is severely limited. Studies must examine whether findings to inform interventions for this population will be useful for most people who experience community reintegration. Addressing these critical gaps, we propose integration of subjective data from EMA with physiology from the Empatica Embrace2, collected in individuals' (N=300) natural settings during the 30 days after residential SUD treatment. Aim 1 identifies features of negative and positive affect dynamics that predict return to use outcomes during community reintegration of SUD inpatients. Aim 2 tests theutility of physiology from a wearablebi...