BACKGROUND AND OBJECTIVES To date, many studies have reported on the association of obesity with gastroesophageal reflux disease (GERD), although none of these have been systematic. In light of this, we conducted this study to examine the association of obesity and GERD. SUBJECTS AND METHODS A total of 3363 patients underwent gastroscopy at Hanyang University Health Promotion Center. Among these patients, we prospectively examined patients who were diagnosed with GERD-related erosive esophagitis on endoscopy. RESULTS Multivariate analysis showed that the significant risk factors were waist-to-hip ratio (WHR), hiatal hernia, body mass index (BMI), and smoking. As compared with patients who had a WHR less than 0.8, the multivariate odds ratio for erosive esophagitis were 4.055 for a WHR more than 1.0 and 2.316 for a WHR of 0.8 to 1.0. As compared with patients who had a BMI of 20 to 22.5, the multivariate odds ratio for erosive esophagitis was 3.308 (95% confidence interval, 1.792 to 6.107) for a BMI greater than 30. CONCLUSIONS Obesity, especially abdominal obesity, was the significant risk factor for erosive esophagitis.