In patients with gastro-oesophageal reflux disease (GORD), oesophageal symptoms and mucosal damage traditionally are related to acid-reflux episodes with pH lower than 4. Oesophageal or extra-oesophageal symptoms of GORD may also be associated with less acidic reflux (pH 4-7). New methodologies have evolved to complement pH monitoring for characterisation of less acidic gastro-oesophageal reflux. This review will focus on definition, detection, pathophysiology and symptom association of weakly acidic and non-acid reflux, in both adult and paediatric populations.