Non-erosive reflux disease (NERD) has emerged as a real entity in the spectrum of gastroesophageal reflux disease (GERD) and may, indeed, represent the most common manifestation of reflux disease. Recent information indicates NERD can be further subclassified based on the results of pH studies and suggests that functional heartburn needs to be differentiated as that subgroup of patients in which there appears to be no relationship between symptoms, however 'typical' of GERD, and acid exposure. Other aspects of NERD need to be appreciated, including overlap with functional dyspepsia and the potential variations in response to such therapeutic interventions as acid-suppressive therapy and fundoplication. It seems quite possible that our failure to separate functional heartburn from NERD, in general, has contributed, in large measure, to diagnostic difficulties and therapeutic disappointment in GERD. An appreciation of the range of entities, of different etiology and pathology, within NERD will foster the development of effective approaches to the assessment and therapy of this challenging disorder.