The recent National Health and Nutrition Examination Survey (NHANES) sampled only the civilian, non-institutionalized population of USA and may have underestimated the prevalence of hepatitis C virus (HCV) in this country. We searched the database MEDLINE, the Bureau of Justice Statistics, Center for Medicare and Medicaid and individual states Department of Corrections for all epidemiological studies regarding the prevalence of HCV in populations not sampled by the NHANES survey namely the incarcerated, homeless, nursing home residents, hospitalized and those on active military duty. Because of their relatively low frequency in the NHANES sample, we also expanded our search to include healthcare workers and long-term dialysis patients. Although included in the NHANES sample, we also performed searches on drug users (injection and non-injection) and veterans to confirm the findings of the NHANES study. Based on the prevalence of studies identified meeting our inclusion criteria, our most conservative estimates state that there at least 142 761 homeless persons, 372 754 incarcerated persons and 6805 persons on active military duty unaccounted for in the NHANES survey. While the NHANES estimates of drug users (both injection and non-injection) appear to be reasonable, the survey seems to have underestimated the number of HCV-positive veterans. Our most conservative estimates suggest that there are at least 5.2 million persons living with HCV in USA today, approximately 1.9 million of whom were unaccounted for in the NHANES survey.