Crohn's ileocolitis is an etiologically unclarified inflammatory disease of the alimentary canal, which is in most cases arranged in segments, may concern all segments, but above all may take place in the inferior ileum and the adjacent segments of the colon. The diagnosis which formerly was certainly made too infrequently is difficult, but histologically it is to be ascertained by typical granulomas of the epitheloid cells. The disease which extraordinarily often is connected with recidivations demands a consequent conservative combination therapy with salazopyrine and cortisone, in acute exacerbations and in formations of fistulae an additional prescription of bactericidal broad spectrum antibiotics is necessary. Resistent courses justify the application of immunosuppressive drugs. The indication to operation is critically to be given and to be restricted to the resection of stenosing narrowings of the lumen.