Murine double minute clone 2 oncoprotein (MDM2) is a key component in the regulation of the tumour suppressor p53. The association between the MDM2 polymorphism and gastric cancer (GC) has been investigated in Turkish population. In the present case-control study, the aim was to investigate the association between genetic polymorphisms of the MDM2 gene (a major regulator of p53 function) and primary GC risk in a Turkish population. The polymorphism, T309G (rs2279744) in the MDM2 gene was determined in patients with GC (n=65) and in healthy control subjects (n=67) using the polymerase chain reaction-restriction fragment length polymorphism method. The findings were evaluated using logistic regression and.2 tests. No statistically significant differences were observed between the control subjects and patients with GC regarding smoking status. A comparison between GC cases and control subjects indicated a statistically significant difference for family history of cancer [odds ratio (OR)=0.17; 95% confidence interval (CI), 0.05-0.56;.2=0.19; P=0.01]. A significant difference was identified in the GG genotype distribution between GC patients and control subjects (OR=4.58; 95% CI, 1.18-17.79; P=0.022). Thus, the results of the present study indicate that the MDM2 gene T309G intron (GG) genotype may be an important risk factor for GC development in the Turkish population.