Background/aims: An association between ineffective esophageal motility and gastroesophageal reflux disease is already known, but there are also some conflicting data. We evaluated the association between ineffective esophageal motility and gastroesophageal reflux disease in patients who underwent ambulatory pH monitoring for the evaluation of reflux symptoms at Gazi University, Gastroenterology Clinic. Materials and Methods: A total of 239 patients who underwent endoscopy, esophageal manometry and ambulatory 24-h pH monitoring due to reflux symptoms were enrolled. Of them, we selected patients who had normal esophageal motility and ineffective esophageal motility. The endoscopy and ambulatory pH monitoring findings were compared between the two groups. Results: Of the 239 patients who presented with reflux symptoms, pathologic acid reflux or endoscopic esophagitis was found in 114 (48%). Ineffective esophageal motility was found in 18 (16%) in the pathologic reflux group and in 4 (3%) in the functional reflux group (p=0.01). Ambulatory pH, manometric and demographic findings were compared in ineffective esophageal motility and normal motility groups. Lower esophageal sphincter (LES) pressures were lower in the ineffective esophageal motility group (19.7 versus 16.2; p=0.01), and total reflux times in both supine and upright position were higher (10.3 versus 4.9; p=0.01) in the ineffective esophageal motility group. Ineffective esophageal motility patients were older and more obese than normal motility group patients. Conclusions: This study points to a clear association between ineffective esophageal motility and gastroesophageal reflux disease as defined by ambulatory pH monitoring.