Ulcerative colitis may occur on several forms. Toxic megacolon is roentgenologically characterized by dilatation usually in the area of transverse colon and toxic symptoms. At the first appearance of these symptoms the patient should be treated or operated upon. Under normal circumstances the roentgenological diagnosis may be obtained only by a full erect or a left lateral decubitus film of the abdomen. A barium enema could lead to performation of the colon, peritonitis or provocation of toxic megacolon. In doubtful cases the examination should be performed with water-solubel contrast media (i. e. Gastrografin, Propyliodon etc.) The therapeutical internal and surgical possibilities are discussed.