Yersinia enterocolitica and Yersinia enterocolitica-like bacteria constitute a fairly heterogenous group of bacteria which includes both well-established pathogens and a range of environmental strains which are ubiquitous in terrestrial and freshwater ecosystems. Pathogenic significance in man is mainly associated with a few serogroups (O:3, O:9, O:8, O:5,27). The pathogenic serogroups show different geographical distributions. The development of isolation procedures which clearly differentiate pathogenic from non-pathogenic variants has been difficult. Of special significance in food hygiene is the ability of Y. enterocolitica to grow in refrigerated foods. There is strong indirect evidence that pigs and food products of porcine origin are the major sources for human infection with Y. enterocolitica serogroups O:3 and O:9, the dominant human pathogens in most parts of the world. The reservoir(s) for serogroup O:8, which prevails in the U.S.A., is uncertain. The pig is the only animal consumed by man which regularly harbours pathogenic Y. enterocolitica. Improved isolation methods and DNA colony hybridization using genetic probes has indicated that the prevalence of pathogenic Y. enterocolitica in pork products is substantially higher than previously suggested. Prevention and control measures should focus on information of people involved in food processing and preparation and on the improvement of hygiene during slaughtering of swine. Important critical control points at the stage of slaughter are: (i) circumanal incision and removal of intestines, (ii) excision of the tongue, pharynx, and particularly the tonsils, (iii) post-mortem meat inspection procedures which involve incision of the mandibular lymph nodes, and (iv) deboning of head meat.