Background Interleukin 28B (IL28B) single nucleotide polymorphism (SNP) genotypes and viral factors can predict sustained virological response (SVR) in HCV genotype-1 (HCV-1) patients receiving 48 weeks of pegylated interferon and ribavirin. Whether these factors would identify those patients who can benefit from a shorter duration of therapy remains unclear. Methods Treatment-naive HCV-1 patients ( n=662) receiving 24 or 48 weeks of combination therapy were enrolled. Baseline demographic data, HCV viral load, IL28B SNP genotypes (rs8099917), duration of therapy and rapid virological response (RVR) were evaluated to predict SVR. The SVR rates were further stratified by the independent factors and compared. Results The IL28B rs8099917 TT genotype, low baseline viral load (HCV RNA≤600,000 IU/ml), RVR and 48-week therapy independently predicted SVR. In RVR patients with the IL28B rs8099917 TT genotype, the SVR rate of 24-week therapy was comparable to 48-week therapy (95% versus 99%; P=0.21) at low baseline viral load, but was inferior to 48-week therapy (70% versus 97%; P<0.001) at high baseline viral load. In non-RVR patients, the SVR rate of 24-week therapy was inferior to 48-week therapy for those with the IL28B rs8099917 TT genotype but high baseline viral load (23% versus 62%; P<0.001), and those with the IL28B rs8099917 GT/GG genotype but low baseline viral load (0% versus 33%; P=0.02). Conclusions HCV-1 patients simultaneously bearing the IL28B rs8099917 TT genotype, low baseline viral load and RVR can benefit from a shorter duration of combination therapy.