Gastroesophageal reflux disease (GERD) is currently defined as "a condition which develops when the reflux of stomach contents causes troublesome symptoms and/or complications". Doctors often diagnose and treat GERD based on symptoms of heartburn and regurgitation. In recent years, the prevalence of partial or non-response to Proton Pump Inhibitors (PPI) has increased resulting in diagnostic testing with esophagogastroduodenoscopy (EGD) or ambulatory pH monitoring. Most patients do not have endoscopic evidence for reflux. Thus, in this group pH monitoring has emerged as an important physiologic test to determine the degree of esophageal acid exposure and to assess the association between patients' persistent symptoms and acid reflux events. The aims of this study are to assess the sensitivity and specificity of symptom associated indices and determine the best parameter for predicting GERD from a list of conventional pH measurement findings.