Objective - The combination of pegylated interferon (PEG-IFN), ribavirin (RBV) and a protease inhibitor (PI) has been approved in summer 2011 for the treatment of genotype 1 (G1) hepatitis C virus (HCV)-infected patients, with a substantially improved efficacy. The aim of this study was to estimate the number of G1 patients to be treated in France in 2012 and associated costs. Methods - A published model of HCV and data on PEG-IFN sales were used to estimate patients needing treatment using three scenarios. (1) HCV screening rate unchanged versus 2010; proportion of treated F0-F1 patients unchanged, proportion of treated F2-F4 patients increased to the current proportion of treated F2-F4 G2/3 patients. (2) Scenario 1 but the proportion of treated F0-F1 patients increased to the current proportion of treated F0-F1 G2/3 patients. (3) Scenario 2 but a 5% increase in the HCV screening rate. To estimate cost, treatment duration was multiplied by drug unit cost. Probabilities corresponding to treatment duration were estimated based on liver fibrosis stage, treatment-naive or experienced status of the patient and virological response kinetics on treatment. Results - Compared with the 5100 G1 patients treated in 2010, the number of G1 patients receiving treatment in 2012 would be 15 000 in scenario 1, 18 300 in scenario 2 and 19 400 in scenario 3, among whom 2.5-3.7% may receive PEG-IFN/RBV and 96.3-97.5% PEG-IFN/RBV+PI. Costs associated with this regimen use ranged from 497 to 638 million Euros. Conclusion - These model-based estimates indicate that new anti-HCV treatments may result in a three- to fourfold increase in the number of G1 patients to be treated in France in 2012. (R.A.)