Many patients with GERD do not experience heartburn symptoms. Barium esophagram, endoscopy and/or overnight esophageal pH monitoring are commonly relied upon to objectively establish the diagnosis of GERD. In general, overnight esophageal pH monitoring is the most sensitive and specific test available to confirm GERD. However, the literature exploring GERD as a cause of chronic cough suggests that the currently accepted criteria for defining abnormal overnight esophageal pH may not be adequately sensitive. It is therefore possible that aggressive GERD therapy may improve asthma control in patients with "normal" overnight esophageal pH probe results. To our knowledge, there are no published data addressing this question.