Several new technologies have been developed to improve the diagnostic capability of conventional endoscopic techniques. One of these most frequently used methods is chromoendoscopy with Lugol's solution in the esophagus to detect malignant lesions. This method has been used for several decades and is generally considered as a safe method, only a few cases of side effects having been reported. We describe a case of acute esophageal and gastric mucosal damage after application of Lugol's solution during endoscopy in an 84-year-old woman. Endoscopists should be aware of the potential for adverse reactions to iodine staining.