Real-world effectiveness data are needed to inform hepatitis C virus (HCV) treatment decisions. The uptake of ledipasvir/sofosbuvir (LDV/SOF) regimens across health care settings has been rapid, but variations often occur in clinical practice. The aim of this study was to assess sustained virologic response (SVR) of LDV/SOF6ribavirin (RBV) in routine medical practice. This observational, intent-to-treat cohort was comprised of 4,365 genotype 1, treatment-naive, HCV-infected veterans treated with LDV/SOF6RBV. SVR rates were 91.3% (3,191/3,495) for LDV/SOF and 92.0% (527/573) for LDV/SOF1RBV (P 5 0.65). African American race (odds ratio 0.70, 95% confidence interval 0.54-0.90, P 5 0.004) and FIB-4 >3.25 (odds ratio 0.56, 95% confidence interval 0.43-0.71, P < 0.001) were independently associated with decreased likelihood of SVR; age, sex, body mass index, decompensated liver disease, diabetes, genotype 1 subtype, and regimen did not predict SVR. In models limited to those who completed 12 weeks of treatment, African American race was no longer a significant predictor of SVR but FIB-4 >3.25 (odds ratio 0.35, 95% confidence interval 0.24-0.50, P < 0.001) remained. Among those without cirrhosis (defined by FIB-4 3.25) and with baseline HCV RNA<6,000,000 IU/mL, SVR rates were 93.2% (1,020/1,094) for those who completed 8 weeks of therapy and 96.6% (875/906) for those who completed 12 weeks of therapy (P 5 0.001). Conclusions: In this real-world cohort, SVR rates with LDV/SOF6RBV nearly matched the rates reported in clinical trials and were consistently high across all subgroups; those without cirrhosis but with HCV RNA<6,000,000 IU/mL were less likely to achieve SVR with 8 weeks compared to 12 weeks of therapy, although the numeric difference in SVR rates was small. (HEPATOLOGY 2016;64:405-414)