Objectives. To describe the prevalence, distribution and risk factors for hepatitis C virus (HCV) infection among homeless adults using eight Health Care for the Homeless (HCH) clinics nationally. Methods. Data were collected for 387 participants through blood draws, structured interviews, chart reviews. Results. Overall prevalence of HCV-antibody positivity was 31.0%, including 70.0% among injection drug users and 15.5% among reported non-injectors. Much HCV infection was hidden as the majority (53.3%) of HCV-antibody positive participants was unaware of their status. Independent risk factors for HCV among the total sample included injection drug use, prison, and tattoos; among injectors, risk factors included prison and three or more years of injection drug use; among reported non-injectors, risk factors included tattoos and prison. Conclusion. These HCH clinics serve high concentrations of HCV-infected injectors, making these and similar clinics priority intervention sites for aggressive screening, education, testing, and treatment for HCV and other blood-borne diseases.