The clinical symptoms of infections with Y. ent. and pseudotub. are of a different nature. Whether the infection becomes apparent in form of a pseudo-appendicitis, enterocolitis or a typho-septic disease does apparently not only depend on the type of pathogens but also on the children's condition with regard to their resistance. All forms mentioned are observed in case of infections with Yersinia pseudotuberculosis as well as in case of infections with Yersinia pseudotuberculosis as well as in case of infections with Yersinia enterocolitica. However, infections with Yersinia enterocolitica seem to have more frequently a chronic course and to be accompanied by conjunctivitis, arthritis and skin diseases. For the subacute and the chronic forms of the disease, a specific treatment is not necessary in most cases. Severe enterocolitis and septicemia, however, need an antibiotic therapy besides the symptomatic therapy. The best antibiotics for an infection with Yersinia enterocolitica still seem to be the tetracyclines and leucomycine, for an infection with Yersinia pseudotuberculosis also the cephalosporines, ampicilline and carbenicilline.