The aim of the study was to assess the susceptibility of 103 Yersinia enterocolitica strains isolated from pigs in Poland in the years 2000-2007 to 12 ß-lactam antibiotics. The in vitro susceptibility of the bacteria to seven selected cephalosporins of all generations and to five penicillins was tested by means of a disk diffusion method following the criteria and recommendations provided by the National Committee for Clinical Laboratory Standards. The strains varied greatly in regard to their in vitro susceptibility- to ß-lactam antibiotics. The strains were found to be relatively highly susceptible to the third and fourth generation cephalosporins, while being generally resistant to the first generation cephalosporins and most penicillins. Taking into account the wide spread of Y. enterocolitica, in particular in the pig population, but also among other animal species, which creates an increasing risk to the public health, it is deemed necessary to systematically monitor the susceptibility of Y. enterocolitica strains to antibiotics.