OBJECTIVES: To compare costs for hepatitis C patients by analyzing retrospective sick fund claims data. METHODS: A representative panel of 1,193,464 patients from several national governmental sick funds were analyzed for 2008. These claims data include all direct medical costs from hospitals, materials in the outpatient sector and medication (covering 60% of sick fund full costs). Selection criteria for patients were at least one confirmed out- or inpatient diagnosis for acute or chronic hepatitis C (ICD-10 GM B17.1 and B18.2). The sample was divided into two groups, those treated with pegylated Interferon/Ribavirin ((peg)INF/Rib) (standard of care for chronic hepatitis C patients according to German guidelines) and those without (identified by ATC Code L03AB and J05AB04). Of these patients all ICD-10 diagnoses were grouped by the DxCG software to hierarchical condition categories in order to calculate risk scores predicting resource use. The expected cost at the average for all insured persons analyzed in this German sick fund panel is represented by a risk score of 2.2. Risk scores and co-morbidities were compared with the sick funds average means. RESULTS: A total fo 2628 hepatitis C patients were identified (0.2% of the panel), 245 with and 2383 without (peg)INF/Rib therapy (treatment rate 9.3%). Sixty-two percent of patients with hepatitis C suffered from at least 11 co-morbidities (risk score 8.5), while only 27% of all other patients from the panel suffered from at least 11 co-morbidities. Further analyses revealed additional pharmacy costs of € 12,200,- for patients treated with (peg)INF/Rib compared to those without. The risk score for the second year after treatment was 5.7 for (peg)INF/Rib-treated versus 8.7 for (peg)INF/Rib-untreated patients. CONCLUSIONS: A diagnosis of hepatitis C is associated with high numbers of co-morbidities and high risk scores. Results suggest that treatment lowers risk scores but keeping them substantially above mean.