Yersinia enterocolitica (Y.e.) is presented from taxonomic point of view. The increased accounts of isolates performed during the last years from both humans and animals are described. Y.e., which is of great interest both in human and veterinary medicine, has been isolated in an increased frequency, from domestic as well as wild animals, from different foods, and also from drinking waters. The modes of transmissions are in many parts unknown, but clinical and epidemiological data suggest that the majority of infections both in humans and animals occur through the digestive tract. From different countries reports have been presented on the assumption that swine are playing an important role as reservoirs for infections in man. Foods contaminated with Y.e. bacteria either, primarily or secondarily, seem to be an important source of infections in the occurrence of Y.e. outbreaks.