Enteral yersiniosis is caused either by Y. enterocolitica 0-group I (syn. serotype 0:3) and 0-group V (syn. serotype 0:9) or Y. pseudotuberculosis type I-VI. The clinical symptoms are mostly like enteritis, enterocolitis, acute abdomen, mesenteric lymphadenitis, or ileitis terminalis. Post-infection reactions are possible like septicemia, arthritis and erythema nodosum. Only cultural and serological examinations confirm the diagnosis of enteral yersiniosis. In the judgement of serological results it is necessary to consider the cross-reactions of Y. enterocolitica 0-group V to Brucella abortus, Brucella melitensis and Brucella suis and also to the antigenic community of Y. pseudotuberculosis type II respectively IV to Salmonella group B respectively D. With exception of septicemia, it is not necessary to treat enteral yersiniosis with antibiotics.