The overall goal of the proposed health services research project is to improve the outcome of medical care for injection drug users (IDUs) with Hepatitis C viral (HCV) infection. This will be done by testing an intervention designed to improve the rate of HCV treatment completion and sustained virologic response (SVR) in IDUs. This intervention will increase access by integrating HCV medical care into a substance abuse treatment program. HCV infection is endemic among IDUs, and is associated with significant medical morbidity. While antiviral treatments are improving rapidly, providing HCV medical care for IDUs remains problematic for a number of reasons. IDUs often do not have adequate access to HCV diagnosis and treatment services, and they may have co-morbid psychiatric diagnoses that affect the ability to withstand the demands of HCV treatment. Therefore, this study will also examine psychiatric disorders and psychiatric symptoms in IDUs who are infected with Hepatitis C virus.