objective: to assess the presence of yersinia enterocolitica in otherwise healthy pigs slaughtered for human consumption. methods: one hundred pharyngeal tonsils were sampled in a slaughterhouse in the state of mexico. the minimum sample size (n=100) was calculated based on a preliminary sample of 20 cases, which had 20% positive cases. the collected tonsil samples were inoculated in rappaport broth, and salmonella-shigella and mcconkey media. the biotyping identification process was based on biochemical and serological tests using o:3, o:8 and o:9 antisera. results: twenty-two isolates were obtained. most were biotype 1 (8 cases of o:3 and 8 cases of o:9), but 6 cases could not be serotyped. none of the isolates were of o:8 group. conclusions: this was the first time that y. enterocolitica serotypes were isolated from pig tonsils in mexico. its importance rely on the fact that the isolated serotypes are the most commonly found in public health problems.