To investigate the influence of the T-to-A polymorphic sequence at position +874 in the interferon (IFN)-gamma gene (+874 IFN-gamma) on the response to combination therapy with high-dose interferon and ribavirin, the single nucleotide polymorphisms were determined by using a polymerase chain reaction sequence-specific primers approach in 150 histologically proved chronic hepatitis C (CHC) patients. The distribution of genotypes for +874 IFN-gamma were T/T: 6 (4.0%), T/A: 31 (20.7%) and A/A: 113 (75.3%) and 24.7% (37/150) of patients were inherited T allele. After undergoing combination therapy with high-dose IFN-alpha and ribavirin, 70.7% (106/150) of patients achieved sustained viral response (SVR). Based on multivariate regression analyses, the independent factors predicting HCV SVR after combination therapy were HCV genotype non-1b (P<0.001) and low pretreatment HCV RNA levels (P=0.041) (odds ratios/95% C.I.: 10.150/4.023-25.609 and 0.581/0.345-0.979, respectively). No association between genotypes, A or T alleles of +874 IFN-gamma and response to combination therapy with high-dose IFN-alpha and ribavirin. In conclusion, we found that with high SVR rates after combination therapy with high-dose IFN-alpha and ribavirin, HCV genotypes and pretreatment serum HCV RNA levels, but not inheritance of the IFN-gamma polymorphism at the position +847, were predictors for SVR.