INTRODUCTION: Despite rising hepatitis C virus (HCV) incidence in the United States in recent years among young adults, little data describe HCV testing in youth. My objective was to characterize the HCV care cascade in adolescents and emerging adults in a large US sample and to describe the association between diagnosed substance use disorders (SUDs) and HCV testing. METHODS: In this retrospective cohort study, I describe HCV care cascade outcomes for youth 13–21 years old seen at least once from 1/2012–9/2017 at an OCHIN-participating federally qualified health center. Using electronic health record data, I analyzed odds of HCV testing by number of concurrent diagnosed SUDs associated with HCV risk (those associated with injection or intranasal use: opioids, amphetamines, and cocaine). RESULTS: Among 269,124 youth who met inclusion criteria, (54.7% female, 62.5% non-white, mean age [SD] at testing 18.5 [2.2] years), 6812 (2.5%) were tested for HCV antibody, 122/6812 (1.8%) of those tested were anti-HCV positive, and of anti-HCV positive youth, 75.4% had additional diagnostic testing. Only 1 had documented HCV treatment. Each additional HCV risk-associated SUD was associated with higher odds of HCV testing, particularly in younger (OR 9.12, 95% CI 6.78, 12.4 in 13–15 year-olds, and OR 8.37, 95% CI 7.48, 9.36 in 16–18 year-olds) compared with older youth (OR 3.9, 95% CI 3.59, 4.24 in 19–21 year-olds). CONCLUSION: This study highlights important gaps in recommended HCV testing during the current opioid crisis. As the first step in the care cascade, addressing missed testing opportunities is critical for reducing hepatitis C burden. / 2020-09-28T00:00:00Z