The potentially functional polymorphism, SNP309, in the promoter region of MDM2 gene has been implicated in cancer risk, but individual published studies showed inconclusive results. To obtain a more precise estimate of the association between MDM2 SNP309 and risk of cancer, we performed a meta-analysis of 70 individual studies in 59 publications that included 26,160 cases with different types of tumors and 33,046 controls. Summary odds ratios （OR） and corresponding 95% confidence intervals （CIs） were estimated using fixed- and random-effects models when appropriate. Overall, the variant genotypes were associated with a significantly increased cancer risk for all cancer types in different genetic models （GG vs. TT： OR, 1.123; 95% CI, 1.056--1.193; GG/GT vs. TT： OR, 1.028; 95% CI, 1.006--1.050）. In the stratified analyses, the increased risk remained for the studies of most types of cancers, Asian populations, and hospital-/population-based studies in different genetic models, whereas significantly decreased risk was found in prostate cancer （GG vs. TT： OR, 0.606; 95% CI, 0.407-0.903; GG/GT vs. TT： OR, 0.748; 95% CI, 0.579--0.968）. In conclusion, the data of meta-analysis suggests that MDM2 SNP309 is a potential biomarker for cancer risk.
