The clinical value of endoscopic ultrasonography (EUS) in the diagnosis of submucosal tumors (SMT) in the upper digestive tract was examined. EUS was performed in 83 patients with SMT or submucosal compressions by extracanal organs or lesions. The 50 cases of SMT and 33 cases of extracanal compression could be diagnosed accurately. All SMT were easily detected, even if they were smaller than 5 mm in diameter. EUS visualized in which of the five layers of the digestive tract wall the submucosal tumor was located and depicted the size of the tumor accurately as confirmed by examination of the resected material. Leiomyoma and leiomyosarcoma originating in the mucosal muscle layer and the proper muscle layer were difficult to distinguish by EUS. The submucosal tumors in the submucosal layer, such as cysts, an aberrant pancreas, fibromas, and lipomas could be diagnosed by the analysis of echogenicity and echo-pattern of the tumor ultrasonograms. EUS was considered to be the most useful method among the conventional body imaging techniques to visualize submucosal tumors.