Background: Polymorphisms of genes encoding cytokines could be potential biomarkers to predict risk of gastric cancer (GC). Here, we investigated the association between the IL-6 -6331 (T/C, rs10499563) polymorphism in its promoter region and GC risk. Methods: In this case-control study of 215 GC cases and 518 non-cancer controls, the IL-6 -6331 (T/C, rs10499563) polymorphism was genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Results: Individuals with the TC or CC genotype were associated with a significantly decreased risk of GC (OR=0.710, 95%CI: 0.504-0.999, P=0.049) compared with TT wild-type carriers. Ther C allele was also associated with significantly decreased risk of GC (OR=0.715, 95%CI: 0.536-0.954, P=0.023) compared with the T allele. In the stratification analysis, TC or CC genotypes were associated with significantly decreased GC risk in subgroups of males, people older than 60, and H. pylori-positive cases. However, no significant interaction was observed for TC or CC genotypes with H. pylori infection. On stratification with the Lauren classification, TC or CC genotypes were associated with significantly decreased risk of diffuse-type GC (OR=0.497, 95%CI: 0.266-0.925, P=0.027), also in subgroups of males, people older than 60, and H. pylori-positive cases. Conclusions: The IL-6 -6331 (T/C, rs10499563) polymorphism is associated with genetic susceptibility of GC and may have the potential to predict GC risk.