PROJECT SUMMARY. The QUIT-Mobile study proposes to use mobile phone self-monitoring and feedback to enhance and sustain over 12-months the impacts of the Quit Using Drugs Intervention Trial (QUIT), an ef- fective screening and brief intervention (SBI) previously successful in reducing risky drug use (i.e., moderate use) in low-income, diverse patients over a 3-month follow up. We propose to conduct the QUIT-Mobile study for primary care patients who receive care in 8 clinics of federally qualified health centers (FQHC) in Southern California over 12-months follow up, comparing to QUIT and Usual Care (UC). The proposed study is an Effec- tiveness-Implementation Hybrid Type 1 design consisting of a single-blind, 3-arm, RCT with adult, mostly La- tino FQHC primary care patients with risky drug use (ASSIST score 4-26), randomized to 3 conditions (n=320/arm, n=960 total): 1) QUIT-Mobile; 2) standard QUIT; 3) Usual Care. Qualitative data on implementa- tion facilitators and barriers will inform future scale-up and sustainability, in addition to cost data and cost-effec- tiveness analysis. The aims are to examine effectiveness in reducing risky drug use and cost-effectiveness comparing the three arms over 3-, 6- and 12-months. Drug use measures include urine drug tests, and timeline follow-back self-reports for past 7-days and past 30-days (risky drug users have sporadic drug use patterns requiring longer self-report recalls for drug use that urine screens may not detect). The 3-arm study enables testing of the independent and synergistic effects of QUIT-Mobile compared to QUIT and both to Usual Care, acknowledging that mHealth components alone may not be effective outside of a clinical/coaching relationship. The 12-month timeline reflects anticipated scale-up scenarios of annual primary care visits when screening and brief intervention would be repeated routinely. QUIT contains 3 components: 1) patient screening with the WHO ASSIST, 2) brief clinician advice (<4 minutes) including opioid overdose prevention education, and 3) 2- and 6-week telephone drug-use health coaching sessions utilizing motivational interviewing and cognitive be- havioral techniques, delivered by paraprofessional health coaches. QUIT-Mobile proposes to test the addition of mobile phone self-monitoring, feedback, and coach monitoring dashboard to enhance and sustain QUIT's drug use reductions using mobile app, text-messaging (SMS), or interactive voice response (IVR) to allow par- ticipation by with varying technological preferences. This study does not test which technology platform is more effective, but rather, the effectiveness of the intervention functions (i.e., self-monitoring, automated feedback, coach monitoring) that are delivered via patients' preferred technologies. This study is novel and timely in inte- grating massively scalable mobile phone tools into an effective primary care BI to prevent substance use disor- der (SUD) in FQHC patients delivered by paraprofessiona...