The frequency of occurrence of Campylobacter jejuni germs in dressed poultry was studied for a year. The samples--smears from the body cavities of chickens--were collected during the technological dressing of the chickens; 101 strains of Campylobacter jejuni (i. e. 28.69%) were isolated from the 352 samples analyzed. The occurrence of the germs exhibited a considerable seasonal variance with peak rates in spring and summer. The use of a suitable culture medium, the technique of cultivation and the properties of the isolated strains were studied at the same time. The culture medium (Agar no. 3 IMUNA enriched with supplement C, horse blood and ingredients increasing the aerotolerance of the germs--sodium pyruvate and iron sulphate) used during the investigation was found to be suitable. The technique of cultivation by means of an anaerostat manufactured by the Development Station in Brno, atmosphere regulation (5% CO2) and with a pre-set cultivation temperature (43 degrees C) was found to be suitable for the screening of the Campylobacter jejuni germs.