Background: This study was to determine whether patients with significant nighttime heartburn had more disturbed sleep and more gastroesophageal acid reflux than those without significant nighttime heartburn. Methods: Thirty-three reflux patients were stratified into 2 groups (nighttime heartburn, without nighttime heartburn). All patients completed questionnaires assessing daytime and nighttime heartburn and subjective sleep by Pittsburgh Sleep Quality Index. All participants underwent 24-hour esophageal pH monitoring and an overnight polysomnographic study. Results: The number of reflux events longer than 5 minutes was significantly greater in patients with nighttime heartburn than in those without nighttime heartburn for the total (P = 0.004) and upright (P = 0.01) position periods. Acid contact time was significantly greater in patients with nighttime heartburn during the upright (P = 0.003) period and during the total (P = 0.001) period. Patients with nighttime heartburn reported significantly greater subjective sleep impairment (8.1 +/- 0.7) than those without nighttime heartburn (6.1 +/- 0.4; P = 0.02), but no difference could be observed in any objective sleep parameter by an overnight polysomnographic study between the groups. Conclusions: Patients with significant nighttime heartburn seem to have more acid reflux compared with those without nighttime heartburn. Nighttime heartburn together with sleep complaints is associated with excessive gastroesophageal reflux.