Experts are anxious because “American serotype” Yersinia entorocolitica O:8 unexpectedly appeared in Europe in the years 2000 because of its high pathogenicity. The aim of the investigations was to determine people risk contact with different serotypes of Yersinia, based on erological investigations in the years 1997–99 in relation to current epidemiological situation. The study covered 573 sera, rom 300 healthy persons and 157 suspicious of yersiniosis, and 116 suspicious of other zoonosis. Tests were performed by passive hemaglutination reaction with antigens viewed as pathogenic to humans Y. enterocolitica O:3, O:5, O:6, O:8, O:9 and Y. pseudotuberculosis group I and III. The most frequently detected antibodies were anti-Y.e. O:5 (41,2%) and then anti-Y.e. O:8 (36,6%), anti-Y.e. O;3 (20,1%), anti-Y.e. O;6 (9,2%), anti-Y.e. O:9 (4,6%) and anti-Y. pseudotuberculosis I i III (11,8% and 10,3%). The results of investigations show, that already in theyears 1997–1999 over 30% of population had contact with Yersinia sticks, including serotypes thought as pathogenic: Y. enterocolitica O:3 (20,1 %), Y. enterocolitica O:9 (4,6 %) and particularly with Y. enterocolitica O:8 (36,6 %).