[Purpose] The current preoperative evaluation for cancerous depth of invasion is carried out by utilizing various examinations, such as radiographic examination (Barium study), normal and chromo-endoscopy, endoscopic ultrasonography, CT and MRI. All of these are very useful, however, the examinations are based on the morph of the tumor. The ultrasonic tactile sensor (UTS) is a newly developed device, which can introduce a new parameter, the stiffness of the tumor, into preoperative evaluation for cancerous depth of invasion. Since the introduction of endoscopic mucosal resection (EMR), the differentiation between mucosal and submucosal cancer is one of the most important points in preoperative examinations in esophageal, gastric and colo-rectal cancers. The authors investigated the clinical usefulness of UTS, especially in superficial esophageal cancers, during endoscopy. [Methods] 21 patients with untreated esophageal cancer were enrolled in this study. Each patient was diagnosed as having esophageal squamous cell carcinoma by histopathological examination of endoscopic biopsy specimen. The thin probe of UTS was utilized in this study. It is 2.4mm in diameter and 2m in length, and can be inserted through the biopsy channel of the endoscope. By measuring the magnitude of the vibrational frequency shift (δf) of transducer, UTS can demonstrate the results as a digital score. The greater the value of magnitude of frequency shift, the softer the tissue. [Results] 31cancerous lesions in 21 patients were measured. UTS demonstrated significant differences between the mean.f value of the mucosal esophageal cancer and submucosal cancer. However, we could not identify the differences between normal esophageal mucosa and mucosal cancer. [Conclusions] The UTS study has a potential to distinguish between mucosal and submucosal cancer, i.e. the differentiation between EMR and other surgical resection.We endeavored to investigate the usefulness of the UTS more precisely now.