The primary aim of this study is to measure and explain the impact on long-term opioid use when medication-assisted treatment (MAT) is bundled with an evidence-based mobile-health system (A-CHESS).

Inclusion Criteria:

1. are 18+ years old;
2. meet criteria for opioid use disorders of at least moderate severity (4 or 5 DSM-V criteria);
3. Are currently taking medication-assisted treatment (MAT) as part of their standard clinical care;
4. have no acute medical problem requiring immediate inpatient treatment;
5. have no history of psychotic disorders, though those with other co-morbid psychopathology (mood disorders, anxiety, other substance use disorders) will be eligible;
6. are willing to participate in a randomized clinical trial;
7. provide the name, verified telephone number, and address of at least 2 contacts willing to help locate the patient, if necessary, during follow-up;
8. are able to read and write in English;
9. are not pregnant;
10. are willing to share health-related data with primary care clinicians; and
11. are, at study intake, abstinent from opioids for at least 1 week and no longer than 2 months, except for medications used to treat the disorder (e.g., methadone).