 Subjects are randomized to undergo UGI endoscopy in either WLE or bright light NBI modes, using a high definition gastroscope Olympus 190 or 290 series. An endoscopy assistant will then open the next numbered sealed envelop at the instruction of the endoscopist. For subjects randomized to WLE, the entire examination will be performed using white light. For subjects randomized to NBI, the NBI mode will be switched on before insertion into the stomach. Once the gastroscope is inserted into the duodenum, the endoscopist can switch back to WLE to examine the duodenal mucosa. Before withdrawal from the duodenum back into the stomach, the NBI mode will be switched on and gastric mucosal examination carried out in the NBI mode. After the gastric examination findings using NBI have been recorded, the endoscopist is allowed to re-examine the gastric mucosa using white light, but any additional findings will not be recorded in the study data sheet. During withdrawal into the esophagus, the endoscopist can switch back to WLE to examine the esophageal mucosa. 