Currently gastrointestinal mesenchymal tumors are divided into three major categories: myogenic tumors(leiomyoma, leiomyosarcoma), neurogenic tumors (schwannomas) and neoplasms that belong to neither group, which are known by GIST(gastrointestinal stromal tumors). The stromal tumors are hetrogenous, so that they may show myogenic or neurogenic differentiation or both, or no differentiation at all in some patients. The best defining feature for GIST is their expression of KIT-protein(CD117). Leiomyomas are the most common mesenchymal tumor in esophagus. Esophageal GISTS are very rare in comparision to those of the stomach and intestine. Recently we experieneced one case of the esophageal GIST, so that we describe an esophageal GIST on immunohistochemical analysis. A 70 years old woman complained of dysphagia and nausea for 3 days. FGS showed a huge elevated lesion in lower esophagus 33cm distal to incisor, which was covered with normal mucosa. CT and UGI showed the intramural tumor of lower third of the esophagus. The distal esophagectomy and esophago-gastrostomy were performed. The tumor was located in lower third of esophagus and measured as $6{ imes}3.7$cm in size. Immunohistochemically, it showed weakly positive CD117 and diffusely positive S-100. SMA, desmin, NES and chromogranin showed negative immune-reaction. The patient was followed for 15 month after operation. There was no recurrence.