The purpose of this study is to evaluate the effectiveness of a simeprevir-containing hepatitis C virus (HCV) treatment regimen as measured by sustained virologic response (SVR).

This is a multicenter, observational (a study in which the investigators/ physicians observe the patients and measure their outcomes), prospective study (a study in which the patients are identified and then followed forward in time for the outcome of the study) designed to reflect routine clinical practice. Approximately 300 Hepatitis C virus (HCV) infected patients who are prescribed simeprevir by their health care provider as part of their routine HCV treatment regimen, inclusive of patients who have been treated with a simeprevir-based therapy for less than or equal to (<=) 28 days will be enrolled in this and observed to evaluate the effectiveness of a simeprevir. Practice setting features will be documented at the initiation of the study by each participating site. The decision of patients to participate in this study will in no way impact upon the standard of care that they are receiving. All treatment decisions will be made at the discretion of the health care provider. Safety assessments will include assessment of adverse events, and clinical laboratory parameters (hematology, clotting tests, human immunodeficiency virus tests, chemistry, and liver function tests). The maximum study duration for each patient will be approximately 2 years.

Inclusion Criteria:

• Patients who have genotype 1 chronic hepatitis C infection
• Hepatitis C virus (HCV) ribonucleic acid (RNA) test result above the limit of quantification before initiation of simeprevir-based therapy
• Health care provider decision to treat patient with a simeprevir-based therapy, inclusive of patients who have been treated with a simeprevir-based therapy for less than or equal to (<=) 28 days will be enrolled into the study
• Prior HCV treatment must be completed more than 3 months before initiation of simeprevir-based therapy
• In the opinion of the health care provider, the patient will attend routine standard of care visits, either at enrolled site or by virtual/telemedicine

Exclusion Criteria:

• Non-genotype 1 HCV infected patients
• Absolute contraindication to any component of prescribed HCV treatment per prescribing information
• Patient is currently enrolled in an interventional study
• Past use of an HCV direct-acting antiviral therapy
• Any investigational drug use within 30 days before initiation of simeprevir-based therapy

Hepatitis C virus (HCV) infected patients receiving simeprevir.