The results of a study on the occurrence of two bacteria that cause zoonoses, Campylobacter spp. and Yersmia enterocolilica were presented and the results of bacteriological and serological methods of detection were compared. The study was carried out on 30 fattening herds in Lower Saxony, Germany Bacteriological findings of Campylobacter spp. in the faeces indicated that 69.7% of the fattening pigs were positive, but 81 .2% tested positive serologically. All herds tested here were both bacteriologically and serologically positive for Campylobacter spp. Furthermore, only 8.4 % tested pos1t1ve for Yersinia enterocolitica in the faecal samples, but 66.8 % of the animals were serologically positive for that bacterium. At herd level 43.3 % of the herds tested bactenologically positive for Yersinia enterocolitica, whereas serological testing showed that 83.3 % of the units had one or more reacting animal.