OBJECTIVES: To estimate the financial impact of currently uninsured individuals infected with chronic hepatitis C (CHC) who will enter the healthcare system in 2014 under the Affordable Care Act. METHODS: Uninsured CHC prevalence estimates among the US household population were obtained by aggregating data from three National Health and Nutrition Examination Surveys (NHANES) conducted between 2005 and 2010.  Commercial insurance claims data from 2007 to 2011 were used to estimate the average annualized all-cause direct medical cost of a CHC patient.  ICD-9 diagnosis codes were used to identify CHC patients.  All medical service and prescription pharmacy costs were tracked longitudinally and subsequently adjusted for inflation and length of enrollment. RESULTS: The prevalence rate of CHC among the US household population was 0.89% during 2005-2010 (95% CI (0.69%, 1.09%)).  A total of 40.12% of these individuals were uninsured (95% CI (32.02%, 48.21%)).  Applying NHANES prevalence rates to US Census Bureau’s current population survey data, the estimated 2011 uninsured CHC population was 1.1MM.  However, only 25% or 275,000 individuals may be diagnosed.  The average annual medical cost for privately insured diagnosed CHC patients was approximately $24,000.  Combining the uninsured CHC prevalence and cost estimates, the annual direct cost of these currently uninsured diagnosed CHC individuals is approximately $6.6B when they enter the health system.  The overall incremental cost of currently uninsured CHC individuals may be even higher due to the cost incurred by the undiagnosed CHC population. CONCLUSIONS: A large proportion of CHC infected individuals are currently uninsured.  When the ACA health insurance mandate takes effect in 2014, this population will gain access to health care coverage and could substantially increase the cost to the healthcare system.