Background: Mdm2 binds to the amino-terminus of p53 to induce its degradation and a single nucleotide polymorphism in the MDM2 promoter region (T309G) has been reported to increase the risk of several carcinomas, such as gastric cancer. However, the results of published studies to analyze the association between MDM2 T309G and gastric cancer havve often conflicted. Methods: To better illustrate the filiation between MDM2 T309G and gastric cancer, we performed a meta-analysis. Odds ratios (ORs) and 95% confidence intervals (CIs) were used to evaluate the strength of the relationship. The pooled ORs were performed for 4 models, additive, recessive, co-dominant model, and dominant. Results: Nine published case-control studies including 3,225 gastric cancer cases and 4,118 controls were identified. The MDM2 T309G polymorphism was associated with a significantly increased risk of gastric cancer risk when all studies were pooled into the meta-analysis (GG versus TT, OR=1.57; 95% CI=1.57-2.12; p=0.003) and GG versus GT/TT, OR=1.52; 95% CI=1.217-1.90; p<0.001). Furthermore, Egger's test did not show any evidence of publication bias (P=0.608 for GG versus TT). Conclusion: Our results suggest that the MDM2 T309G polymorphism is indeed associated with a significantly increased risk of gastric cancer.