ED-INNOVATION is currently recruiting, training, and providing resources to 30 Emergency Department (ED) sites throughout the U.S. to implement ED-initiated buprenorphine (BUP) for patients presenting with untreated opioid use disorder (OUD). ED-INNOVATION is a pragmatic randomized clinical trial (RCT) comparing the effectiveness of sublingual buprenorphine (SL-BUP) versus a 7-day extended-release formulation of buprenorphine (XR-BUP) in 2000 patients with untreated OUD will be conducted in sites achieving competence (e.g. demonstrating ability to enroll patients with OUD and adhere to protocols for administering both formulations of buprenorphine). The primary outcome will be engagement in formal addiction treatment within 7-days post ED visit. Engagement in formal addiction treatment on the 30th day post randomization and cost effectiveness is also being studied.