It is widely accepted that chromoendoscopy using Lugol's solution is effective for the detection of early esophageal squamous neoplasia. However, this modality may cause severe chest pain and discomfort owing to mucosal irritation. The conventional concentration of Lugol's solution is in the range of 1.2% to 2.5% . Image quality can be guaranteed with this range of Lugol's solution. However, lead to retrosternal pain and discomfort, and can even induce erosion or ulceration in the esophagus and stomach. This study was to test whether a lower concentration of Lugol's solution, which has minimal mucosal irritation, can provide satisfied image quality by a randomized blinded controlled trial.