From July 1989 to June 1990, a total of 19 patients with gastric polyps were studied by magnifying endoscopy and dye endoscopy. After pretreatment with pronase, both close and magnified pictures were observed before and after sprays of 0.2% indigo carmine. Polypectomy or multiple biopsies were done after endoscopic examinations. Of the 19 patients; 13 were classified as hyperplastic polyps and 6 as neoplastic polyps by histologic examination. Twelve of the 13 hyperplastic polyps showed regular sulciolar or sulciolar-mesh mucosal patterns after magnification, only 1 showed an irregular sulciolar-mesh pattern. All 6 neoplastic polyps showed irregular or destructive mucosal patterns. Hyperplastic polyps have a significantly higher rate of regular, fine gastric mucosal patterns. Contrast staining with indigo carmine did not significantly improve the observations. We conclude that magnifying endoscopy is useful in the diagnosis of gastric polyps; polyps with fine, regular gastric pits indicate a diagnosis of hyperplastic polyps, while irregular or destructive mucosal patterns suggest a high possibility of neoplastic polyps.