Sleep disturbances are commonly reported by patients who suffer from gastroesophageal reflux disease (GERD) but it is uncertain if GERD plays a role in patients with sleep disorders of undetermined origin. The prevalence of GERD in patients with sleep disorders of unknown etiology is uncertain; the aim of this study was to determine this prevalence. Three hundred eighty-five consecutive patients reporting to an outpatient clinic for evaluation of sleep disorders were assessed for their sleepiness in relation to reflux symptom intensity. Reflux symptoms that met the survey criteria for a diagnosis of GERD were present in 45 of the 385 subjects (12.8%). These subjects did not have a diagnosis of GERD and were not being treated. Multiple regression analysis showed that excessive sleepiness was associated with intensity of GERD symptoms. Patients with GERD had significantly higher Epworth sleep scores than patients without GERD (12.8 vs. 10.6; p=0.007), indicating more daytime sleepiness. We conclude that unrecognized and untreated GERD are present in many patients presenting with sleep disorders. Patients with GERD had significantly greater sleepiness. Further studies of the impact of GERD treatment in this population are necessary.