Gastroesophageal reflux disease (GERD) is a common disorder in Western countries. For many years our attention has been focused on patients with erosive esophagitis, but in recent times we have realized that endoscopy-negative reflux disease is the most common presentation of this illness, affecting up to 70% of these individuals. Patients with the non-erosive form (NERD) are a heterogeneous group including various subpopulations with different mechanisms for their main symptom of heartburn: reflux of acidic and non-acidic gastric contents, mucosal hypersensitivity, intraesophageal distension by gas, intraduodenal infusion of fat, muscle contractions and psychological abnormalities. As to esophageal acid exposure, patients with NERD can be subdivided into those with abnormal and normal pH testing. The latter group includes patients with a positive correlation between symptoms and reflux events, in whom heartburn can be controlled by proton pump inhibitor (PPI) therapy. According to the recent Rome III criteria, they are still in the realm of GERD. An additional group is called functional heartburn, because this typical symptom is associated neither with an abnormal pH test nor with a positive symptom index. Their response to PPIs is very disappointing. Therefore, there is an increasing consensus on the fact that they do not have GERD and should be treated with drugs other than PPIs.