The purpose of this guidance is to assist sponsors in the clinical development of direct-acting antiviral (DAA) drugs for the treatment of chronic hepatitis C (CHC) from the preinvestigational new drug application (pre-IND) stage through the new drug application (NDA) and postmarketing stages. For the purposes of this guidance, the Food and Drug Administration (FDA) defines direct-acting hepatitis C virus (HCV) antivirals as drugs that interfere with specific steps in the HCV replication cycle through direct interaction with the HCV genome, polyprotein, or polyprotein cleavage products. Specifically, this guidance addresses the FDA’s current thinking regarding the overall development program and clinical trial designs to support DAA drugs. The organization of this guidance parallels the drug development plan.