Virulence factors such as hydrophobicity of cell surface, capsule formation and slime production were investigated in 393 CNS strains, 190 isolated from bovine mastitis and 203 from human infections; in addition a selected number of CNS species were experimentally infused into the teat cistern of lactating rabbits for pathogenicity tests. Most human (95%) and bovine (82.6%) strains showed cell hydrophobicity properties, however only 11.3% and 7.9% were capsulated strains, respectively. Slime production was detected in 10.5% of bovine strains but only in 0.9% of human strains. Using the lactating rabbit model it was shown that S. chromogenes, S. epidermidis, S. saprophyticus and S. haemolyticus were the most pathogenic species.