This is the examination of the esophagus, stomach and the duodenum with a flexible fiberoptic tube which is passed through the mouth. Direct visual inspection can identify hiatus hernia, esophageal diverticula, inflammation, ulcers and tumors of the esophagus, stomach and duodenum. Biopsy of suspicious lesions can be done and microscopic examination of these biopsies can help to diagnose ulcer and tumor. Material effects, risks and side effects: perforation of esophagus, stomach, and duodenum; bleeding from biopsied site; aspiration pneumonia.