This is an Open-label Phase 3 study in subjects with chronic genotype 1, 2 and 3 HCV-infection who are co-infected with HIV-1. A total of 230 (115 genotype 2/3 and 115 genotype 1) HIV-1/HCV co-infected subjects will be enrolled into one of 3 treatment regimens depending on their genotype and prior HCV treatment history.

Subjects will be treated with oral sofosbuvir 400 mg once daily plus weight based ribavirin (RBV) (1000 or 1200 mg/day) twice daily for 12 weeks or 24 weeks. The study population will include genotype 1, 2, and 3 treatment-naive subjects (including interferon [IFN] ineligible) and genotype 2 and 3 treatment-experienced subjects who have failed prior therapy with pegylated interferon (PEG)/RBV. Approximately 20% of the subjects enrolled will have evidence of compensated cirrhosis at Screening.