This attacks the mucous membranes mainly, and this is diffuse nonspecific inflammation of unknown cause which often forms erosions or ulcers. The appellation and concept which Council for International Organization of Medical Science (CIOMS) of WHO defined are, as follows. (1973) Mainly this attacks the mucous membrane and submucosal layers, the idiopathic, non-specific inflammatory diseases in the colon especially rectum are seen, in mostly adults who are 30 years old or under, also seen in children or the age group over 50 years old. The cause is unknown, and involvement of the immunopathological mechanism or psychological factors are suggested. Usually bloody diarrhea and various degrees of systemic symptoms are presented. When it attacks throughout the entire colon for a long time it tends to become malignant.