Bacterial biofilms are a big problem in medicine and food industry. A bacterial urce of contamination in a food chain, it presents a problem as a mechanical obstacle and it is very difficult to remove. Aggregational capability of bacteria and bacterial surface hydrophobicity are key factors for the formation of biofilm. Microbiological aggregation is necessary for microcolony formation, while bacterial surface hydrophobicity is related to bacterial adhesiveness. This is a virulent trait of bacteria. We used different strains of Campylobacter jejuni. This bacteria is a common cause of zoonoses, a disease which spreads directly or indirectly from animals to people. In the experiments, we compared different strains and their combinations in a test of aggregation with measuring optical density and a later calculation of aggregation and co-aggregation. The level of bacterial adhesiveness on a polystyrene surface was evaluated with using Kristal violet staining and plate counting. Results showed that bacterial aggregation of C. jejuni is a strain-specific trait. Bacterial co-aggregation is different from the capability of bacterial aggregation of individual strains. Our results did not confirm that the capability of bacterial aggregation and co-aggregation is in correlation with the capability of bacterial adhesiveness and co-adhesiveness.