Esophagitis caused by reflux is one of the most frequent diseases diagnosed by endoscopy of the upper gastrointestinal tract. Reflux may be physiological. The main pathological conditions causing reflux are the hiatus hernias and sequelae of surgical procedures. Esophagitis occurs exclusively in the layer of stratified epithelium. In early stages it presents as white stripes of erosion with a typical red frame or as a peptic lesion. The colors red or white are dependent upon depth of the process, coating and stage of healing. Pathogenesis, various forms of manifestation, and complications of the reflux disease can be understood if one knows about mucosal metaplasias which may occur. This metaplastic process involves replacement of areas of stratified epithelium by cylindrical epithelium. Peptic stenosis located highly in the esophagus usually indicates a distal segment of cylindrical epithelium. The so called endobrachyesophagus (Barrett esophagus) occurs in rare cases congenitally - it can be also found after complete healing of the esophagitis without any signs of inflammation or stenosis. Therefore it seems appropriate to introduce an additional classification for the Barrett esophagus (E0, EI-IV). The reflux disease is clinically important because of its tenacious clinical symptomatology and its complications. Endobrachyesophagus has been recognized as a precancerous condition and should be controlled regularly.