The prevalence of eosinophilic oesophagitis appears to be increasing in many countries, sometimes rapidly, although this may be partly due to increased disease recognition. Histological methods of assessment and diagnostic criteria vary considerably between major clinical centres. Oesophagitis with over 20 intraepithelial eosinophils per high power field is more likely to be due to allergy than gastro-oesophageal reflux induced acid-peptic mucosal injury. Typical eosinophilic oesophagitis shows involvement of the entire oesophagus, with basal cell proliferation occupying more than 50% of the thickness of the surface epithelium, and high numbers of intraepithelial eosinophils, sometimes concentrated on the surface or as contiguous clusters. Ulceration and prominent neutrophils are atypical and should suggest an alternative or co-existent disease. On endoscopy, the oesophagus may display the typical 'corrugated' mucosal appearance. Clinically, dysphagia or food impaction are the most characteristic symptoms. There is a strong association with other atopic diseases, especially asthma and eczema. To date no evidence has emerged of an increased malignancy risk. Patients with eosinophilic oesophagitis typically fail to respond to acid suppressive medications but respond well to either elemental/elimination diets or aerosolised swallowed corticosteroids. Long-term uncontrolled oesophageal eosinophilic inflammation may lead to progressive subepithelial fibrosis, potentially resulting in strictures or oesophageal narrowing.