A Phase 3B Randomized, Open-Label, Multi-Center Trial Assessing Sofosbuvir + Ribavirin for 16 or 24 Weeks and Sofosbuvir + Pegylated Interferon + Ribavirin for 12 Weeks in Subjects With Genotype 2 or 3 Chronic HCV Infection.

Study start date: September 24, 2013

Key Inclusion Criteria: * Male or female, age greater than or equal to 18 years. * Confirmed chronic HCV infection. * Subjects will have cirrhosis status assessment; liver biopsy may be required. * Genotype 2 subjects must have cirrhosis of the liver to be eligible. * Treatment-naive or prior treatment failure to ≥12 weeks of an interferon- based regimen that was not discontinued prematurely due to an adverse event * Infection with HCV genotype 2 or 3 as determined at Screening * Body mass index (BMI) greater than or equal to 18 kg/m\^2 * Screening laboratory values within predefined thresholds. * Liver imaging (e.g., ultrasound) within 6 months of Baseline/Day 1 is required in cirrhotic patients to exclude hepatocellular carcinoma (HCC). In the event of intrahepatic lesions, triple phase CT scan or MRI should be performed to exclude HCC. * Subject must be of generally good health as determined by the Investigator. Key Exclusion Criteria: * Prior use of any other inhibitor of the HCV nonstructural protein (NS)5B polymerase * Pregnant or nursing female or male with pregnant female partner * History of any other clinically significant chronic liver disease. * HIV or chronic hepatitis B virus (HBV) infection. * Malignancy with the exception of certain resolved skin cancers. * Chronic use of systemically administered immunosuppressive agents. * Clinically-relevant drug or alcohol abuse. * History of solid organ transplantation. * Current or prior history of clinical hepatic decompensation. * History of clinically-significant illness or any other major medical disorder that may interfere with subject treatment, assessment or compliance with the protocol. * Known hypersensitivity to interferon, RBV, the study investigational medicinal product, the metabolites, or formulation excipients. Note: Other protocol defined Inclusion/Exclusion criteria may apply.