Before surgery, 12 patients with suspected leiomyoma and 12 patients with suspected leiomyosarcoma were studied by endoscopic ultrasonography (EUS), computed tomography (CT), endoscopy, and barium swallow. The results were correlated with surgery and histology. Ten leiomyomas, one benign gastric ulcer, one carcinoid metastasis, eight leiomyosarcomas, two leiomyoblastomas, one mucus secreting adenocarcinoma, and one bronchial carcinoma were diagnosed. Eighteen additional patients suspected to have benign submucosal lesions by endoscopy and barium meal were treated non-surgically, and studied by EUS and CT. EUS was superior to other imaging techniques in the detection, staging, and follow-up of submucosal smooth muscle tumors because of clear imaging of the intramural abnormality and adjacent lymph nodes.