The clinical value of endoscopic ultrasonography (EUS) in the diagnosis of submucosal tumors (SMTs) of the stomach was examined. We used echo endoscopes with a 7.5 or 10.0 MHz radial-scan transducer made by Olympus Co. Ltd. EUS was carried out on 80 patients with SMTs of the stomach including 54 cases confirmed histologically (24 cases of leiomyoma, 3 of leiomyosarcoma, 12 of cysts, 7 of aberrant pancreas, 4 of lipoma, 2 of carcinoid, and 3 of other diseases). Fifty-nine patients with extraluminal compression were detected by endoscopy and/or x-ray examination. We examined the effectiveness of EUS based on our analysis of the gastrointestinal tract wall seen in the EUS image as a five-layered structure corresponding with that of the histological layers. As a result, SMTs and extragastric compression were easily distinguishable in the EUS images of the lesions. The size, location, and origin of the SMTs could be detected. From the location of the SMT in the five-layered structure seen in the EUS image we could predict its histological nature. Thus, EUS was a most valuable method not only in the diagnosis of intramural and extramural SMTs but also in the detection of extragastric compressive lesions and organs.