OBJECTIVES: To characterize the demographics and comorbidities of US Medicare beneficiaries diagnosed with chronic hepatitis C virus (HCV) infection. METHODS: This study was based on 2005-2010 CMS Fee-for-Service Medicare longitudinal claims data which includes 100% of the adjudicated medical claims for all inpatient and outpatient institutional providers and a 5% sample of adjudicated patient claims from the physician office setting.  ICD-9 codes were used to identify patients diagnosed with chronic HCV infection as well as the following comorbidities: anxiety, depression, alcohol abuse, HIV, and end stage renal disease (ESRD). RESULTS: A total of 368,871 chronic HCV patients were identified as having received Medicare benefits between 2005 and 2010.  The average age of these chronic HCV patients in 2010 was 57.2 (SD=11.7) which is 14 years younger than the non-HCV Medicare population (average = 71.0, SD=13.0). Only 28.4% of chronic HCV patients qualified for Medicare due to age alone (≥65 years old) versus 82.0% of non-HCV patients.  The majority of chronic HCV patients (63.4%) qualified for Medicare due to a disability that excludes ESRD, while only 16.9% of non-HCV patients met the same criteria.  Chronic HCV patients exhibited a wide array of health problems.  The prevalence rates of comorbidities such as anxiety (15.2% vs. 4.8%), depression (26.8% vs. 7.6%), alcohol abuse (40.9% vs. 2.1%), HIV (8.1% vs. 0.3%) and ESRD (8.5% versus 1.3%) were higher (all statistically significant, p<0.0001) in the chronic HCV population than the non-HCV population. CONCLUSIONS: Medicare beneficiaries are often generalized as over 65 years of age, but chronic HCV Medicare patients are typically younger and qualify for Medicare due to disability. The burden of patients with chronic HCV on Medicare is further exacerbated by the high prevalence of other costly comorbidities.