SUMMARYBackground: Studies suggest obstructive sleep apnea syndrome (OSAS) frequently manifests in patients with gastroesophageal reflux disease (GERD) and that there may be a causal relationship. Aim: To determine the relationship between OSAS and symptoms of GERD. Methods: Consecutive patients referred to the Sleep Disorders Center (SDC) 18 years and older with polysomnographically defined OSAS were evaluated prospectively for GERD using a validated symptoms questionnaire. The GERD and OSAS relationship was assessed by 1) determining frequency of GERD in patients with and without OSAS; 2) ascertaining the relationship between