To determine the epidemiological characteristics of Japanese patients with gastroesophageal reflux disease(GERD), we investigated the prevalences of heartburn, reflux esophagitis(RE), hiatus hernia and Barrett's mucosa, and assessed the correlations among them. In total, 15.4 % (725/4,723) of patients had heartburn twice or more per week and 42.2% had symptoms of heartburn, including those who had heartburn once or less per week, and 16.7 % (602/3,608) of patients had RE. The prevalences of hiatus hernia and Barrett' s mucosa were 49.3 % (1,263/2,560) and 20.8% (536/2,577), respectively. There was a weak correlation between RE and heartburn, but 75.5% of patients who had heartburn did not have any endoscopic abnormalities, and 40.1% of patients without endoscopic abnormalities had heartburn, suggesting the presence of endoscopy-negative GERD. Results also showed that 26.2 % of patients had RE associated with hiatus hernia, and there was a correlation between the two. There was a weak correlation between Barrett' s mucosa and RE and between Barrett' s mucosa and hiatus hernia.