Objective: to test the value of treatment of gasteroesophageal reflux disease (GERD) in improving the obstructive sleep apnea syndrome (OSAS). Patients and methods: The study included 63 patients diagnosed with OSAS after complete history taking, Epworth sleepiness scale (ESS), physical examination, and full night polysomnography. Of them 29 patients were diagnosed with concomitant GERD by standardized Reflux Disease Questionnaire (RDQ), upper endoscopy, and 24-hour pH monitoring and received Pantoprazole 40 mg once daily for 2 months. The patients were reevaluated by polysomnography, ESS, quality of life SF36 v2 questionnaire. Results: The twenty- nine patients with OSAS and GERD had significantly higher body mass index (BMI), waist circumference, and reported non significant increase in sleep and daytime symptoms of OSAS. After 2 months treatment with Pantoprazole, there was significant decrease in apnea hypopnea index (AHI), snoring events, arousal index, and ESS. Meanwhile, there was a significant improvement in sleep efficiency, minimum O2 saturation, desaturation index and quality of life parameters (SF 36 v2). Conclusions: GERD and OSAS are common co morbid conditions. Adequate treatment of GERD with Pantoprazole, 40 mg/day for 2 months was effective in improving many subjective and objective findings of OSAS. In patients with OSAS and history suggestive of GERD, upper endoscopy, pH monitoring and treatment with proton pump inhibitors (PPIs) may be an important adjunct in controlling OSAS symptoms.