The adhering capability and biofilm growth facilitate staphylococcal colonization of surfaces of damaged tissues and foreign bodies. Biofilm-forming bacteria are more resistant to immune system activities, mechanical effects of blood flow and other adverse effects, e.g. those due to antibiotics. Minimal inhibitory concentrations (MICs) were compared for two groups of Staphylococcus epidermidis strains isolated from blood cultures. Group 1 included biofilm positive strains whose biofilm-forming potential was revealed by both phenotypic and genotypic methods. Group 2 included strains without biofilm-forming potential. The comparison of MICs for selected antibiotics showed higher resistance of biofilm positive compared to biofilm negative strains. The difference was evident particularly for oxacillin, tetracycline, co-trimoxazole and gentamicin.