TheUsersofopioidsubstances,especiallyinjectingdrugs,areathighriskofinfection with blood- borne viruses,such as hepatitis B,C and human immunodeficiency virus, due to the sharing of needles and injection equipment. Methadone substitution treatment is approven device in the risk reduction strategy of hepatitis B,C and HIV infection.The aim of this studyis to determine: the socio-demographic and medical psychiatric characteristics of patients with hepatitis B,C and HIV under methadone,the prevalence of hepatitis C,B and HIV,the dose of methadone and compliance with treatment in this population. Materials and methods: This is a retrospective descriptive study of patients admitted to the center of addictology at the hospital Ar-razi of Sale in Morocco , specifically in methadone unit. Results: The prevalence of hepatitis C, B and HIV were respectively 80%, 13% and 4% in patients with positive serology, the average dose of methadone was higher than the dose of all patients enrolled in the methadone program. 80% of patients under methadone with positive serology to HCV, HBV and HIV had a polyconsumption of psychoactive substances (cannabis, cocaine, alcohol, benzodiazepine). 72% of our patients with hepatitis C received treatment for their infection while all the patients with HIV were put on antiretroviral drugs with good therapeutic compliance. Conclusion:Methadone substitution therapy has proven to be a successful strategy to reduce the risk of HIV, HCV and HBV infection in opioid-dependent patients. However, the adjustment of methadone doses and systematic screening for HIV, HCV and HBV is essential in this vulnerable population.