We investigated the association of 5 tagging single nucleotide polymorphisms (SNPs) of MDM2 with chemotherapy-related toxicities and clinical outcomes in 663 patients with advanced nonesmall-cell lung cancer. We identified 2 SNPs (rs1470383 and rs1690924) with significant associations with chemotherapyrelated toxicities. One SNP rs1470383 also influenced the overall survival of patients without overall toxicity or hematologic toxicity. Introduction: Platinum agents can cause the formation of DNA adducts and induce apoptosis to eliminate tumor cells. The aim of the present study was to investigate the influence of genetic variants of MDM2 on chemotherapy-related toxicities and clinical outcomes in patients with advanced nonesmall-cell lung cancer (NSCLC). Materials and Methods: We recruited 663 patients with advanced NSCLC who had been treated with first-line platinum-based chemotherapy. Five tagging single nucleotide polymorphisms (SNPs) in MDM2 were genotyped in these patients. The associations of these SNPs with clinical toxicities and outcomes were evaluated using logistic regression and Cox regression analyses. Results: Two SNPs (rs1470383 and rs1690924) showed significant associations with chemotherapy-related toxicities (ie, overall, hematologic, and gastrointestinal toxicity). Compared with the wild genotype AA carriers, patients with the GG genotype of rs1470383 had an increased risk of overall toxicity (odds ratio [OR], 3.28; 95% confidence interval [CI], 1.34-8.02; P ¼ .009) and hematologic toxicity (OR, 4.10; 95% CI, 1.73-9.71; P ¼ .001). Likewise, patients with the AG genotype of rs1690924 showed more sensitivity to gastrointestinal toxicity than did those with the wild-type homozygote GG (OR, 2.32; 95% CI, 1.30-4.14; P ¼ .004). Stratified survival analysis revealed significant associations between rs1470383 genotypes and overall survival in patients without overall or hematologic toxicity (P ¼ .007 and P ¼ .0009, respectively). Conclusion: The results of our study suggest that SNPs in MDM2 might be used to predict the toxicities of platinum-based chemotherapy and overall survival in patients with advanced NSCLC. Additional validations of the association are warranted.