Background and Aims: Non-alcoholic fatty liver disease (NAFLD) is a hepatic manifestation of the metabolic syndrome and has rapidly increased in Japanese population. Reflux esophagitis has the same trend of increase, and its relation with obesity and metabolic diseases was reported in previous papers. The aim of this study is to clarify the relationship between NAFLD and reflux esophagitis in Japanese subjects. Methods: Among subjects undergone general health examinations 261 NAFLD patients (Group A) and 621 control subjects (Group B) were selected; Group A was defined as sonographically detected fatty liver patients who consumed less than 20 g alcohol per day and Group B as subjects with normal liver image in ultrasound regardless of alcohol consumption. Group A and B were compared with each other regarding the means of BMI, liver test (AST, ALT), blood pressure, serum total cholesterol, serum triglyceride, fasting blood sugar, and HbA1c, as well as the prevalence of reflux esophagitis, its endoscopic severity (LA classification), and association ratio of hiatal hernia. Results: The mean age and sex ratio were 60.2 ± 10.0 yr, M:F = 113:148 in Group A, and 60.0 ± 10.4 yr, 282:339 in Group B, respectively (p = n.s). BMI in Group A (25.8 ± 3.2 kg/m2) was extremely higher than that in Group B (22.8 ± 2.6 kg/m2) (p < 0.0001). AST and ALT levels between Group A and B were 26.8 ± 11.8 vs 23.1 ± 8.3 IU/L, 31.8 ± 20.5 vs 21.5 ± 12.5 IU/L, respectively; the AST/ALT ratio was significantly lower in Group A than Group B (p < 0.0001). Blood pressure was 130.5 ± 20.2/78.8 ± 9.8 vs 125.1 ± 18.8/76.1 ± 10.7 mmHg (p < 0.001). Serum cholesterol and triglyceride were 213.5 ± 33.9 vs 206.9 ± 31.7 mg/dl, 121.8 ± 60.5 vs 92.6 ± 46.9 mg/dl, respectively (p < 0.01, p < 0.0001). Fasting blood sugar and HbA1c were 105.6 ± 28.1 vs 98.4 ± 21.7 mg/dl, 5.55 ± 1.11 vs 5.20 ± 0.72% (p < 0.005, p < 0.0001). All metabolic markers were significantly higher in NAFLD group than in control group. The prevalence of reflux esophagitis was markedly higher in Group A (19.2%) than in Group B (8.9%) (p < 0.0001); however, there were no significant differences in endoscopic severity between Group A and B: 78.0%, 72.7% (grade A), 18.0%, 21.8% (grade B), 4.0%, 5.5% (grade C), and 0.0%, 0.0% (grade D) (p = n.s). Among patients with reflux esophagitis, hiatal hernia was associated more frequently in Group A (72.0%) than Group B (49.1%) (p < 0.05). Conclusion: NAFLD patients were commonly associated with obesity, abnormal liver test, hypertension, hyperlipidemia, and impaired glucose tolerance. The significant high prevalence of reflux esophagitis in NAFLD patients suggested a close relationship between NAFLD and reflux esophagitis in Japan.