AIM: To clarify whether insulin resistance and metabolic syndrome are risk factors for erosive esophagitis.METHODS: A case-control study was performed using the database of the Kangbuk Semsung Hospital Medical Screening Center.RESULTS: A total of 1679 cases of erosive esophagitis and 3358 randomly selected controls were included.Metabolic syndrome was diagnosed in 21% of the cases and 12% of the controls (P＜0.001).Multiple logistic regressions confirmed the association between erosive esophagitis and metabolic syndrome (Odds ratio,1.25; 95% CI,1.04-1.49).Among the components of metabolic syndrome,increased waist circumference,elevated serum triglyceride levels and hypertension were significant risk factors for erosive esophagitis (allP＜0.01).Furthermore,increased insulin resistance (Odds ratio,0.91; 95% CI,0.85-0.98)and fatty liver,as diagnosed by ultrasonography (odds ratio,1.39; 95% CI,1.20-1.60),were also related to erosive esophagitis even after adjustment for a series of confounding factors.CONCLUSION: Metabolic syndrome and increased insulin resistance are associated with an increased risk of developing erosive esophagitis.