Barrett`s esophagus is a metaplasia of the esophageal epithelium of any Length, such that normal squamous epithelium is replaced by specialized columnar epithelium with goblet cells. It is important to diagnose and survey Barrett`s esophagus because it is believed to be the major risk factor for development of esophageal adenocarcinoma. However, the prevalence of Barrett`s esophagus in Korea is Low. Mixed connective tissue disease (MCTD) is a systemic disorder in which patients have combinations of the clinical features of systemic Lupus erythematosus, systemic sclerosis, and polymyositis. Although gastroesophageal reflux disease is common in esophageal involvement in MCTD, Long-segment Barrett`s esophagus in MCTD has not been reported in Korea. We report here a 15 cm-Long segment of Barrett`s esophagus extending to the proximal esophagus in a female patient who has had MCTD for 2 years, and we review the Literature. (Korean J Med 2012;82:73-77)