Hepatitis C affects approximately 180 million people worldwide and is currently one of the main causes of chronic liver disease. HCV infection progresses to chronicity in up to 80% of infected individuals, from whom approximately 20% progress to cirrhosis over 20 years. These individuals are at risk of developing hepatic failure and/or hepatocellular carcinoma. OBJECTIVES: To compare treatment costs and outcomes of peginterferon-alfa-2a versus peginterferon-alfa-2b, both associated with ribavirin, in the therapeutic scheme of 24 weeks for hepatitis C in Brazilian private market for the treatment of HCV infection genotypes 2/3. METHODS: To project disease progression, a Markov model was built based on clinical stages of chronic disease.  A Delphi panel was conducted to evaluate direct medical resources related to each stage, followed by micro-costing of the results. The perspective was from a private payer. Source used for costing was medical society physicians fee list (CBHPM-2008). Drug acquisition costs for a 70kg patient were obtained from official public sources (Kairos Magazine-Nov2009). Costs were reported in 2009 Brazilian Reais (US$1≈$Brz1.7). Efficacy of pegylated-interferons was obtained from a meta-analysis of 7 RCTs comparing the drugs, detailed elsewhere. For genotype 2/3, median rate of sustained virological response was 79.2% for peginterferon-alfa-2a and 73.8% for peginterferon-alfa-2b. Discount rate for costs and outcomes was 5%, according to Brazilian guidelines for HTA. RESULTS: Assuming a lifetime perspective, expected costs and outcomes for peginterferon-alfa-2a were $Brz48,363, 15.21LYs and 14.57QALYs; for peginterferon-alfa-2b, $Brz52,154, 15.11LYs and 14.32QALYs. Cost-effectiveness analysis estimated an ICER of -$Brz37,614/LY and -$Brz15,556/QALYs for peginterferon-alfa-2a, being the dominant therapy. For each 1000 patients treated with peginterferon-alfa-2a instead of peginterferon-alfa-2b, savings granted can be up to $Brz3,8 million which would allow treatment of 78 more patients. CONCLUSIONS: These findings suggest that treatment with peginterferon-alfa-2a is more effective and less costly when compared to peginterferon-alfa-2b under private payer perspective in Brazil.