Aims:Adaptive structure enhancement in endoscopy is effective fordefining the microstructure of the mucosal surface and superficial blood vessels. We conducted a study to assess the utility of this approach for endoscopic investigation of the upper gastrointestinal tract. Subjects and Methods:From July 1996 until June 1997, a total of 1443 cases undergoing upper gastrointestinal endoscopy were randomly divided into imaging positive (730 cases) and negative (703 cases) groups and compared for capacity to detect and diagnose gastrointestinal diseases. The instrument used for adaptivestructure enhancement was the Olympus EVIP-230. We performed upper gastrointestinal endoscpy using Q230 (Olympus Co.Ltd.) with and without the EVIP 230. Results:With regard to endoscopic screening, the numbers of demonstrated disease cases were 318 and 298 for the positive and negative groups, respectively. Among the positive group we detected 2 early gastric cancers, 16 gastric ulcers, 15 duodenal ulcers and others. In the negative groupwe detected 2 early gastric cancers, 13 gastric ulecrs, 4 duodenal ulcers and others. Detection of cases with clear irregularitiesof the mucosal surface and erythema demonstrated tended to be slightly higher in the positive group, but the number of biopsies did not differ between the two groups. When we examined the patients with known disease, for example malignantcases, it was useful in clarifiying the border between the tumor and surrounding normal tissue in esophageal and gastric cancers, as well as determining the extent of invasion. With gastric and duodenal ulcers, erythema and the structure of regenerative epithelium could be clarifiedso that a strict classification of stages was possible. Conclusion:Adaptive structure enhancement is effective for the precise delineation of lesions by endoscopy in the upper gastrointestinal tract. However, there was no significant difference in detecting malignancy when we used the screening endoscopy with or without this enhancement system.