The overall objective of this study is to determine whether high-resolution imaging of the esophagus during routine diagnostic upper endoscopy can assist clinicians in detecting and discriminating dysplastic (precancerous) areas. This high-resolution microendoscope (HRME) was developed by our collaborators at Rice University and provides > 1000x magnified images of the esophageal mucosa. The purpose of this study is to determine whether this device can be used to enhance the diagnostic accuracy of routine endoscopic screening for squamous cell cancer of the esophagus.