The cell surface hydrophobicity is one of the non specific factors of adhesion influencing the ability of microorganisms to colonize nasopharynx. The aim of this paper was to evaluate via salt aggregation test (SAT) the cell surface hydrophobicity of 150 strains of gram-negative rods isolated from the throat or/and nasal specimens of healthy people. It has been found that among the nonfermenting rods hydrophobic strains were predominant. In contrast, the isolates of Enterobacteriaceae family were characterized by the distinctive features of the cell surface within particular genera or even species. The obtained results show that, despite differences in cell surface hydrophobicity, numerous species of gram-negative rods have the ability to colonize the mucous membrane of upper respiratory tract. This suggests that the cell surface hydrophobicity is rather a feature of species or genus, but it is not related to the ecological niche of microorganisms in human body.