The normal esophageal mucosa creates a protective epithelial barrier that constrains the acidic reflux in the esophageal lumen. Microscopic findings and functional studies indicate that this barrier might be impaired in patients with non erosive reflux disease(NERD) but not in patients with functional heartburn(FH). Whereas endoscopy and pH monitoring are the most important diagnostic tools in the diagnosis of NERD, recent studies suggest that esophageal biopsies might have a complementary role. Particularly in the differential diagnosis between NERD and FH, the application of histological severity scores showed very promising results. Further evaluation of the scores could lead to routine application of histology in specific NERD populations. The normal esophageal mucosa creates a protective epithelial barrier that constrains the acidic reflux in the esophageal lumen. Microscopic findings and functional studies indicate that this barrier might be impaired in patients with non erosive reflux disease (NERD) but not in patients with functional heartburn (FH Whereas endoscopy and pH monitoring are the most important diagnostic tools in the diagnosis of NERD, recent studies suggest that esophageal biopsies might have a complementary role. Particularly in the differential diagnosis between NERD and FH, the application of histological severity scores showed very promising results. Further evaluation of the scores could lead to routine application of histology in specific NERD populations.