This study is being done to assess the safety, pharmacokinetics (PK) and pharmacodynamics (PD) of MK-8325 in male hepatitis C virus (HCV)-infected participants. There will be 3 parts to this study. Part I will enroll only genotype 1 (GT1) HCV patients, Part II will enroll only genotype 3 (GT3) HCV-infected participants, and Part III will enroll only GT1a HCV-infected participants. All parts may run concurrently, or may be staggered as needed by the clinical sites.

Inclusion criteria:

• Body mass index (BMI) of 18 to ≤37 kg/m^2
• Diagnosis of chronic HCV infection
• Must be infected with HCV GT1a, GT1b, or GT3

Exclusion criteria:

• Co-infection with GT1 and GT3 HCV
• History of stroke, chronic seizures, or major neurological disorder
• History of clinically significant endocrine, gastrointestinal (excepting HCV infection), cardiovascular, hematological, immunological, renal, respiratory, or genitourinary abnormalities or diseases
• History of neoplastic disease
• Positive Hepatitis B surface antigen
• History of human immunodeficiency virus (HIV) infection or positive HIV serology
• Major surgery, donated or lost 1 unit of blood (approximately 500 mL) or participated in another investigational study within 4 weeks prior
• History of significant multiple and/or severe allergies (including latex allergy), or anaphylactic reaction or significant intolerability to prescription or non-prescription drugs or food
• Current regular user (including "recreational use") of any illicit drugs or history of drug (including alcohol) abuse within approximately 2 months
• Evidence or history of chronic hepatitis not caused by HCV including but not limited to non-HCV viral hepatitis, non-alcoholic steatohepatitis (NASH), drug-induced hepatitis, autoimmune hepatitis
• Previous treatments(s) with nonstructural 5A (NS5A) protein inhibitors
• Treatment with protease inhibitor(s) <30 days prior to study enrollment
• Previous exposure to interferon-alpha and/or ribavirin within 3 months prior to the first dose of MK-8325 in the study
• Clinical or laboratory evidence of advanced or decompensated liver disease; evidence of bridging fibrosis or higher grade fibrosis (Metavir score ≥3) from prior liver biopsy