The Lugol staining method has lately come to play an important role in the detection of superficial esophageal cancers which are extremely difficult to detect by using only a barium double-contrasted esophagiogram and conventional esophagioscopy. Thus we have tested an endoscopy-guided plan of radiotherapy for detecting an esophageal cancer using Lugol stain. This method was found useful in detecting intraepithelial small lesions, such as intramural metastasis or multiple origin cancers. Additionally, it has been found useful in determining the definite shape of superficial malignant lesions by evaluating biopsy specimens taken from the border of the non-stained regions.