Leiomyosarcoma of the stomach is comparatively rare occurrence. We experienced a case which was so difficult in establishing the diagnosis of whether leiomyosarcoma or leiomyoma clinically and pathologically. The patient, a 53 years old man, came to the hospital, complaining of a bout of hematemesis and melena. Clinically, the tumor assumed the form of leiomyoma, except comparatively large 2 ulcerations on the top of this lesion which were strongly suspected of leiomyosarcoma. Histology showed slight immature myogenic tumor cells with large nuclei and slightly eosinophilic cytoplasm. But, atypism and cell division were rarely observed. Therefore, histologically, we could not diagnose of malignant tumor. However, from the clinical view point, leiomyogenic tumor originating from digestive tract is more or less malignant, because of the presence of the metastasis to the general, in spite of the lack of atypism. Therefore, we suspected this case was boderline between leiomyoma and leiomyosarcoma.