In this phase 3 study involving patients with HCV genotype 1, 2, 4, 5, or 6 infection, including those with compensated cirrhosis, treatment with 12 weeks of sofosbuvir and velpatasvir resulted in a sustained virologic response in 99% of patients. The hepatitis C virus (HCV), a single-stranded RNA virus of the family Flaviviridae with six major genotypes, infects up to 150 million people worldwide. 1 , 2 Chronic HCV infection causes progressive liver fibrosis, which can lead to cirrhosis, hepatic decompensation, and hepatocellular carcinoma. 3 , 4 As many as half a million people die annually from liver disease associated with chronic HCV infection. 5 In recent years, the development of drugs that directly interfere with HCV replication has revolutionized HCV treatment. There are now effective combinations of direct-acting antiviral agents for most patients, but in choosing an appropriate regimen, clinicians must take into account . . .