Standard magnifying endoscopy has around 100 fold magnifying power. Intra-epithelial papillary capillary loop (IPCL) pattern is diagnosed with it. Narrow band imaging system (NBI) is extremely useful to recognize IPCL well as a brown spot. In IPCL type classification, type I mainly includes normal epithelium. Type Il corresponds to inflammatory change or non-neoplastic tissue and type Ill reflects border line lesions. Type IV strongly suggests carcinoma in situ. Type V-1 is definitely diagnosed as carcinoma in situ. Endocytoscopy has around 500 fold magnification, which enables observation of cell and nucleus. Endocytoscopic images are classified into 5 categories from normal epithelium to malignant tissue as endocytoscopic atypism classification (ECA classification). ECA IV and V are considered to be treated in clinical setting.