recruitment strategy: Following methods will be used to recruit participants: 1) Brochures and flyers will be distributed in community outreach, general and mental hospitals, NGO-run communities, colleges and universities, drop-in centers and specialized clinics for treatment of participants with HIV and hepatitis C 2) Posters (same content as a brochures and flyers) of the study will be stuck in the billboard of bus/subway, local stores, hospitals, NGO-run communities, colleges and universities, as well as any specialized health-care center for psychiatry or addiction treatments 3) there are two main NGO-run communities in Tehran for treating opiate dependent patients in Tehran. Investigators will use the initial contact letter to recruit from new patients attending these communities for receiving treatment.