Abstract： Objective To investigate the relationship of the single nucleotide polymorphism (SNP) of interleukin-18 (IL-18) gene promoter region-607C/A and-137G/C loci and response to interferon (IFN) treatment in patients with chronic hepatitis C (CHC).Methods A total of 199 CHC patients received combination therapy of IFNα or PegIFNα and Ribavirin in the First Affiliated Hospital,Shanxi Medical University from September 23rd,2005 to August 20th,2012 were enrolled.And 180 healthy subjects were recruited as controls.The SNPs of IL-18 gene promoter region-607C/A and-137G/C loci were detected by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP).Genotype distribution,allele frequency,and the relationships between SNPs in-607C/A and-137G/C loci and response to IFN treatment were analyzed byx2 test.Results-137GG genotype distribution and-137G allele frequency were significantly higher in CHC patients than those in healthy controls (x2 =6.612 and 6.476,P =0.010 and 0.011),whereas-137GC genotype was the opposite (x2 =5.548,P =0.019).Patients with -607AA genotype had higher sustained virological responses (SVRs) to IFN treatment compared with those with-607CA or-607CC genotypes (x2 =4.195 and 5.230,P =0.041 and 0.022).And patients with -607A allele had higher SVRs to IFN treatment compared with those with-607C allele (x2 =5.903,P =0.015).Patients with-137GC genotype had higher SVR to IFN treatment compared with those with-137GG genotype (x2 =5.869,P =0.015),and patients with-137C allele had higher SVRs to IFN treatment compared with those with-137G allele (x2 =3.885,P =0.049).Conclusions Patients with-607AA and -137GC genotypes have higher SVRs to IFN treatment than those with other genotypes.-137G allele seems to be associated with the susceptibility to HCV infection,while-607A and-137C alleles may be correlated with higher SVR to IFN treatment.