Overexpression of cyclooxygenase (COX)-2 has been implicated in the development of cancer. This study aimed to evaluate the relationship between genetic variants in COX-2 promoter interacting with Helicobacter pylori and the susceptibility to gastric cancer (GC). Three COX-2 polymorphisms −1290A>G (rs689465), −1195G>A (rs689466), and −765G>C (rs20417) were genotyped in 323 GC patients and 944 controls. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated by logistic regression model. In GC patients, the ORs were 2.33 (95% CI = 1.50–3.63) and 2.70 (95% CI = 1.68–4.33) for −1195AA and −765CG genotype carriers, respectively. Haplotype analysis showed all −1195A allele-containing haplotypes, except G−1290–A−1195–G−765, were associated with increased risk for GC, compared with the A−1290–G−1195–G−765 haplotype. Moreover, significant multiplicative and additive interactions were observed between H. pylori infection and all these three polymorphisms, and H. pylori-infected subjects carrying the variant allele of −1290A>G, −1195G>A, or −765G>C had increased risk of GC compared with non-H. pylori-infected subjects with wild-type allele (OR = 4.10, 95% CI = 1.90–8.83; OR = 3.46, 95% CI = 1.31–9.11; and OR = 3.32, 95% = 1.27–8.73, respectively). Our results suggested that the COX-2 promoter polymorphisms were associated with increased risk of GC, especially interacting with H. pylori infection. © 2011 Wiley Periodicals, Inc.