BACKGROUNDDirect-acting antivirals (DAAs) are recommended for the treatment of hepatitis C virus (HCV) infection in patients treated with methadone or buprenorphine.AIMTo assess HCV treatment rates in an Opioid Treatment Program (OTP).METHODSThis longitudinal study included 501 patients (81.4% men, median age: 45 years; interquartile range: 39-50 years) enrolled in an OTP between October 2015 and September 2017. Patients were followed until September 2019. Data on socio-demographics, substance use, HCV infection, human immunodeficiency virus (HIV) infection and laboratory parameters were collected at entry. We analyzed medical records to evaluate HCV treatment. Kaplan-Meier methods and Cox regression models were used to analyze the DAA treatment uptake and to identify treatment predictors.RESULTSPrevalence of HCV and HIV infection was 70% and 34%, respectively. Among anti-HCV-positive (n = 336) patients, 47.2%, 41.3%, and 31.9% used alcohol, cannabis, and cocaine, respectively. HCV-RNA tests were positive in 233 (69.3%) patients. Twentyeight patients (8.3%) cleared the infection, and 59/308 (19.1%) had received interferon-based treatment regimens before 2015. Among 249 patients eligible, 111 (44.6%) received DAAs. Treatment rates significantly increased over time from 7.8/100 person-years (p-y) (95%CI: 5.0-12.3) in 2015 to 18.9/100 p-y (95%CI: 11.7-30.3) in 2019. In a multivariate analysis, patients with HIV co-infection were twice as likely to receive DAAs (HR = 1.94, 95%CI: 1.21-3.12) than patients with HCV mono-infection. Current drug use was an independent risk factor for not receiving treatment against infection (HR = 0.48, 95%CI: 0.29-0.80).CONCLUSIONHCV treatment is evolving in patients with HCV-HIV co-infection. Ongoing drug use while in an OTP might negatively impact the readiness to treat infection.