Abstract/Text: Barrett's oesophagus is associated with severe reflux disease and is a risk factor for oesophageal adenocarcinoma. However, there is a lack of consensus on how to assess the presence and extent of Barrett's oesophagus in clinical practice. A diagnosis of Barrett's oesophagus is currently based on the recognition of an abnormal oesophageal mucosa at endoscopy. However, a diagnosis cannot be made solely on this basis, and a true diagnosis requires the identification of an area suspicious for columnar metaplasia at endoscopy, followed by histological confirmation. Currently, difficulties in the assessment of Barrett's oesophagus include a lack of consistent definitions of endoscopic landmarks (such as the gastro-oesophageal and squamo-columnar junctions), a lack of standardization of descriptions of the extent of Barrett's oesophagus, and limited communication between the endoscopist and the pathologist, which hampers accurate histological confirmation. It is therefore important to develop an endoscopic description of Barrett's oesophagus, with a clear definition of endoscopic landmarks, to determine, amongst other things, whether anti-reflux therapy produces regression or a reduction in the length of Barrett's oesophagus. With this background, a subgroup of the International Working Group on the Classification of Oesophagitis was charged with developing a simple, practicable classification system, suitable for use with standard endoscopes, which would be easy to apply in clinical practice and in large clinical studies. Described in this review are a series of propositions and an overview of the 'CM classification', developed by the International Working Group on the Classification of Oesophagitis, to facilitate the endoscopic description of Barrett's oesophagus. It is hoped that these propositions will be the first step in the development of standard endoscopic diagnostic criteria for Barrett's oesophagus, relevant to clinical practice and clinical research.