In dual (PEG-IFN + RBV) HCV therapy RBV concentrations were associated with efficacy and toxicity. Also in former studies in HCV-infected patients treated with telaprevir (TVR) or boceprevir (BOC) in combination with PEG-IFN, the plasma concentration of RBV was associated with Sustained Virologic Response (SVR) and anaemia (defined as Hb<8,5 g/dL). We have tried to determine an optimal therapeutic range for RBV when combined with these DAAs. The plasma concentration of RBV at week 8 should be 2.2-5.3 mg/L in combination with TVR. 48% of the HCV patients in the cohort had these plasma concentrations of which 81% achieved SVR and 5.2% reported anaemia. In combination with BOC the plasma concentration should be 2.2-3.6 mg/L, 50% of patients had these concentrations. In this group 69% of patients achieved SVR and 46% anaemia. So, for these therapies, therapeutic ranges for RBV could be defined for the optimal SVR rates and the lowest incidence of anaemia 6, 7.