OBJECTIVES: The purpose of this study is to evaluate cost-effectiveness and cost-utility of peginterferon alfa-2a (PEGASYS) plus ribavirin (PEGIFN+RIB) versus no treatment, in HIV/HCV co-infected patients in Portugal. METHODS: A 9-state Markov model was developed to simulate the disease progression based on the APRICOT clinical trial population (40-year old patients with HIV/HCV co-infection; genotypes 1, 2/3 and 1/2/3) using the METAVIR scoring system to stage liver disease. The model included the following health states: no fibrosis; portal fibrosis, no septa; portal fibrosis, few septa; septal fibrosis, no cirrhosis; cirrhosis; decompensated cirrhosis; hepatocellular carcinoma; liver transplant and death. The fibrosis progression rates, transition probabilities and quality of life estimates were obtained from reference studies. Efficacy in terms of sustained virological response for PEGIFN+RIB therapy was obtained from APRICOT clinical trial. A lifetime horizon was considered. The analysis assumes the National Health System perspective. Portuguese clinical practice was characterized from a consensus experts panel, including patients’ diagnosis and follow-up, genotype distribution and main resources used. Unit costs were obtained from official data. Costs and outcomes were discounted by three percent annually. One-way sensitivity analysis was performed on non-HCV treatment costs, time horizon, genotype distribution, discount rate and non performing transplant. RESULTS: In the combined analysis, considering the expected genotypic distribution for the Portuguese population, treatment with PEGIFN+RIB was estimated to increase discounted life expectancy by 1.61 years (23.30 vs 2169) and quality-adjusted life expectancy by 1.17 QALYs compared to no treatment. Direct costs were projected to be €29,410 with PEGIFN+RIB and €33,788 with no treatment. These results corresponded to ICERs of -€2.19 and -€3742 per life year gained and per QALY gained, respectively. CONCLUSIONS: The use of of PEGIFN+RIB (PEGASYS/COPEGUS) vs no treatment in patients with HIV/HCV co-infection is a cost-saving (dominant) alternative in the Portuguese setting for all genotypes.