The therapy of gastroesophageal reflux disease (GERD) is uncomplicated in most cases. However, 20 % of GERD patients suffer from reflux-associated symptoms under therapy with proton pump inhibitors (PPI). The cause of this resistance to PPI-therapy remains unclear. Today, the most discussed theory is the presence of the non- or weakly acidic reflux. Objective measurements of the weakly/non-acidic reflux are available since the development of intraluminal impedance monitoring in combination with pH-monitoring. The therapy of weakly/non-acidic GERD is not well established, so far. In the course of clinical studies the therapeutic spectrum (i. e. modification of the medical therapy, endoscopic anti-reflux procedures or surgical therapy) has to be tested.