Chronic hepatitis C affects approximately 180 million people worldwide being one of the main causes of chronic liver disease. About 20% of patients with chronic hepatitis C can develop cirrhosis over 20 years, thus presenting risk of developing hepatic complications. Treatment is currently based on pegylated-interferon-alfa-2a or alfa-2b plus ribavirin. Sustained virologic response (SVR) is associated with a better prognosis compared to untreated patients and treatment failures. OBJECTIVES: To compare treatment costs and outcomes of peginterferon-alfa-2a versus peginterferon-alfa-2b, both plus ribavirin, in the therapeutic scheme of 48 weeks for hepatitis C genotype 1 in Brazilian Public Health System (SUS). 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 results. Perspective was from a public payer. Costing was based on government reimbursement procedures list (SAI/SIH–SUS). Drug acquisition costs (70 kg patient) were obtained from ’Banco de Preços em Saúde’, government source. Costs were in 2009 Brazilian Reais (US$1≈$Brz1.7). Efficacy of pegylated-interferons was obtained from a meta-analysis of 7 RTCs comparing the drugs, detailed elsewhere. For genotype 1, SVR median rate was 42.1% for peginterferon-alfa-2a and 33.3% for peginterferon-alfa-2b. Discount rate (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 $Brz36,713, 14.51LYs and 12.89QALYs; for peginterferon-alfa-2b $Brz41,191, 14.35LYs and 12.49QALYs gained. Cost-effectiveness analysis estimated an ICER of -$Brz27,266/LY and -$Brz11,277/QALY 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 $Brz4,4 million which would allow treatment of 120 more patients. CONCLUSIONS: Findings suggest that treatment with peginterferon-alfa-2a is more effective and less costly when compared to peginterferon-alfa-2b under SUS perspective in Brazil.