There are some problems as to chromo-endoscopy. To resolve this point, we believe NBI will be one of the tools supporting the endoscopic diagnosis of Barrett's esophagus. By only changing the optical filters for sequential lighting from the conventional broadband type to the narrow band type, NBI system can be installed. Through our clinical evaluations as to Barrett's mucosa, we confirmed NBI has an advantage over a conventional system with the representation of the important observation and diagnosis such as the capillary and the fine mucosal structure.