Lugol's iodine chromoendoscopy is an important method to detect esophageal squamous cell carcinoma. Sodium thiosulfate solution (STS) has been used to neutralize iodine after Lugol's chromoendoscopy; however, it is not available in many medical centers. The aim of the current study was to assess the efficacy of N-acetylcysteine solution (NAC) for relieving symptoms caused by Lugol's iodine chromoendoscopy.