The paper presents an epidemiological analysis of 8,232 cases of yersiniosis caused by Y. enterocolitica 03 over 1972-1988 as reported by Hygienic Stations. The steady epidemiological characteristics of yersiniosis were the prevalence of children and boys and a typical seasonal pattern with differences between the Czech and Slovak Republics. In the Czech Republic, there were several incidence peaks following, when summarized, the incidence curve of other alimentary infections, whereas in the Slovak Republic morbidity reached its peak during winter months. The numbers of isolated strains oscillated significantly between districts and by years. It appears that the number of positive findings in different districts is not only an objective value reflecting a mosaic-like pattern of incidence but also depends on the quality of microbiological diagnostics.