BackgroundSyringe services programs (SSPs) provide a spectrum of health services to people who use drugs, with many providing referral and linkage to substance use disorder (SUD) treatment, and some offering co-located treatment with medications for opioid use disorder (MOUD). The objective of this study was to review the evidence for SSPs as an entry point for SUD treatment with particular attention to co-located (onsite) MOUD.MethodsWe performed a scoping review of the literature on SUD treatment for SSP participants. Our initial query in PubMed led to title and abstract screening of 3587 articles, followed by full text review of 173, leading to a final total of 51 relevant articles. Most articles fell into four categories: (1) description of SSP participants’ SUD treatment utilization; (2) interventions to link SSP participants to SUD treatment; (3) post-linkage SUD treatment outcomes; (4) onsite MOUD at SSPs.ResultsSSP participation is associated with entering SUD treatment. Barriers to treatment entry for SSP participants include: use of stimulants, lack of health insurance, residing far from treatment programs, lack of available appointments, and work or childcare responsibilities. A small number of clinical trials demonstrate that two interventions (motivational enhancement therapy with financial incentives and strength-based case management) are effective for linking SSP participants to MOUD or any SUD treatment. SSP participants who initiate MOUD reduce their substance use, risk behaviors, and have moderate retention in treatment. An increasing number of SSPs across the United States offer onsite buprenorphine treatment, and a number of single-site studies demonstrate that patients who initiate buprenorphine treatment at SSPs reduce opioid use, risk behaviors, and have similar retention in treatment to patients in office-based treatment programs.ConclusionsSSPs can successfully refer participants to SUD treatment and deliver onsite buprenorphine treatment. Future studies should explore strategies to optimize the implementation of onsite buprenorphine. Because linkage rates were suboptimal for methadone, offering onsite methadone treatment at SSPs may be an appealing solution, but would require changes in federal regulations. In tandem with continuing to develop onsite treatment capacity, funding should support evidence-based linkage interventions and increasing accessibility, availability, affordability and acceptability of SUD treatment programs.