Evaluation of hydrophobic properties of 309 strains of Acinetobacter calcoaceticus was performed by a SAT method. Among investigated strains cultured at 22 degrees C, 103 strains were autoaggregating, representing very strong hydrophobic properties. Most of strains aggregated at concentration of 0.4-1.0 M (NH4)2SO4, exhibiting strong hydrophobic activities. Only 38 strains during culture at 22 degrees C exhibited hydrophilic surface properties. Differences between strains of anitratus variety and lwoffii variety were noted. Most auto-aggregating strains, in comparison to number of strains isolated from individual materials, were isolated from purulent materials. It is worth attention that hydrophobic activities were also present in strains isolated from nonclinical materials. Microorganisms of this group cultured at 22 degrees C auto-aggregated in as much as 50%, whereas this occurred during culture at 37 degrees C only in 26%.