OBJECTIVE Neoplastic lesions in the digestive-tract mucosa are termed "superficial" when the depth of invasion is limited to the mucosa and submucosa. The endoscopic appearance has a predictive value for invasion into the submucosa, which is critical for the risk of nodal metastases. METHODS The endoscopic morphology of superficial lesions can be assessed with a standard video endoscope after spraying of a dye--an iodine-potassium iodide solution for the stratified squamous epithelium, or an indigo carmine solution for the columnar epithelium. In 2002, a workshop was held in Paris to explore the relevance of the Japanese classification. The conclusions were revised in 2003 in Osaka in relation to the definition of the subtypes used in endoscopy and the evaluation of the depth of invasion into the submucosa. In Japan, the description of advanced cancer in the digestive-tract mucosa using types 1 - 4 is supplemented by a type 0 when the endoscopic appearance is that of a superficial lesion. Type 0 is divided into three categories: protruding (0 - I), nonprotruding and nonexcavated (0 - II), and excavated (0 - III). Type 0 - II lesions are then subdivided into slightly elevated (IIa), flat (IIb), or depressed (IIc). Nonprotruding depressed lesions are associated with a higher risk of submucosal invasion. After endoscopic resection, invasion into the submucosa is an important criterion for the necessity of additional surgical resection. Micrometer analysis of the depth of invasion in the specimen is more precise, and distinct cut-off limits have been established in the esophagus, stomach, and large bowel. CONCLUSIONS The morphology of superficial and nonprotruding neoplastic lesions is relevant to the prognosis. Following endoscopic detection, the lesions are analyzed using chromoendoscopy and assigned a subtype of the type 0 classification. The choice between endoscopic or surgical treatment is based on this description.