Using European data from patients included in the Named Patient Program (NPP) and from the early post-marketing authorization period, the present study aims to describe patient characteristics and to describe the effectiveness of Daclatasvir (DCV)-based regimens in Europe. This will be a retrospective cohort study of patients who received treatment with a DCV-based regimen in the following context: - Patients enrolled within the European NPP in one of the following countries Austria, Denmark, Italy, Sweden, Spain, Switzerland, United Kingdom; or - In those countries where DCV is commercially available (ie, Sweden, Germany, United Kingdom), patients who received DCV during the early post-marketing authorization period The results of this study will contribute to a better understanding of effectiveness of DCV-based regimens in a population that differs from population in the clinical trials, and therefore will provide additional valuable information to inform clinical practice. This study intends to estimate primarily the effectiveness of DCV-based regimens as measured by the sustained virologic response at post treatment follow-up visit week 12 (SVR12). As well as estimate the effectiveness of DCV-based regimens as measured by SVR12 after the end of Hepatitis C virus (HCV). This study intends also to describe as secondary objectives the characteristics (ie, demographic and clinical characteristics and treatment patterns of patients starting a new DCV-based regimens) of patients receiving DCV as well as the effectiveness of DCV-based regimens as measured by: - On-treatment virological response at post treatment follow-up visit Week 4; and - Virological response at the end of treatment (EOT); and - The sustained viral response at post treatment follow-up visit Week 4 (SVR4) and post treatment follow-up visit Week 24 (SVR24); and - The occurrence of virological failure (on-treatment and relapse). An exploratory objective will be to assess the concordance between SVR4 and SVR12 among the overall population treated with DCV.