The analysis of a series of 1,225 cases of reflux esophagitis shows the serious nature of this condition. A liberal use of antireflux operations therefore seems justified. Extensive columnar metaplasia of the distal esophagus, or columnar-lined lower esophagus (CLLE), represents a late irreversible stage of reflux esophagitis. Repeated esophagoscopies demonstrate the acquired nature of the lesion. It is caused by the progressive healing, from below upward, of peptic ulcerations on the squamous epithelium by metaplasia of columnar mucosa. Antireflux operations stop the progressive ascent of heterotopic epithelium and thus stabilize reflux esophagitis and cure complications such as ulcerations and strictures. The premalignant character of this condition is established by a 10 per cent incidence of adenocarcinomas in a series of 140 cases of extensive columnar metaplasia. The transition toward malignancy seems to be irreversible and cannot be arrested by an antireflux operation. Therefore, repeated esophagoscopic controls and biopsies are an absolute necessity in all cases of extensive columnar metaplasia, even after cure of active reflux esophagitis by Nissen fundoplication.