Opioid use disorder (OUD) is a common, underrecognized, undertreated, and deadly medical condition. Although the focus of addressing the opioid epidemic has been centered in the outpatient setting, hospitalists play an important-and often underutilized-role in identifying OUD, initiating treatment, and assisting with linkage to longitudinal care after discharge.Over the past 20 years, the annual rate of hospital discharges documenting OUD has quadrupled. 1 During 2010-2016, the annual discharge rate for heroin overdoses increased by 23%. 1 Although the total number of hospitalizations in the United States remained stable from 2002 to 2012, the number of admissions for opioid abuse or dependence increased from 301,707 to 520,275. More than 500,000 hospital admissions per year (1% of total nationwide hospitalizations) are now due primarily to OUD. 2 Injection opioid use increases the risk of endocarditis, osteomyelitis, septic arthritis, and epidural abscesses, conditions that often prolong hospitalizations and frequently lead to readmissions. Admissions for OUD-related infections are rising at a startling rate. Between 2002 and 2012, the number of admissions for infections associated with OUDs had increased from 3,421 to 6,535. 2 In addition to providing the opportunity to diagnose OUD, hospitalizations offer an ideal time to engage patients in OUD treatment and linkage to outpatient care.Although we uniformly offer patients antibiotic treatment for acute infection, hospitalists should consistently incorporate treatment of OUD to address the root cause of these admissions. As infection is but one sequelae of the underlying disease of addiction, treating without medications for OUD (MOUD) would be akin to treating a diabetic foot ulcer with antibiotics and not providing medications to improve glycemic control. Omitting such addiction treatment can contribute to treatment failure and worse health outcomes. Among patients with endocarditis and an associated valve repair, those who continue injection drug use have a 10 times higher risk of death or reoperation between 90 and 180 days after repair than those not engaged in drug use. 3 Despite data demonstrating the significant benefit and the minimal harm of MOUD, significant gaps remain in providing MOUD and linking patients from the hospital to community care. 1,4 Hospital encounters are missed opportunities to provide life-saving MOUD treatment; the majority of patients with OUD do not receive evidence-based treatment while inpatient. 5 Rosenthal et al. found that of 102 patients admitted with injection drug use-associated infective endocarditis from 2004 to 2014, only 8% received MOUD, and approximately half had a documentation of substance use treatment in their discharge worksheet. 4 In Massachusetts, among individuals who experienced a nonfatal opioid overdose and had interaction with healthcare services, only 26% were on MOUD one year later. 6 Based on our experience, a substantial proportion of patients with OUD do not seek or have access to medical care, acut...