We propose to study prospectively 68 patients who have been identified as positive with mAb DAS-1 immunostaining without histological evidence of specialized columnar epithelium ("True Barrett's" epithelium) during routine endoscopy for dyspepsia or GERD symptoms. These patients have been studied for initial screening for antibody staining under IRB protocol #1698. This number is based on the statistical analysis by Fisher's exact test and has 90% power to detect a 30% negativity (mAb Das-1 positive to negative) at a p<0.05 level. During participation in IRB Protocol #1698, initial biopsy specimens were taken at: