The effect of preincubation of Pseudomonas aeruginosa in subinhibitory concentrations (1/4 x minimum inhibitory concentration) of amikacin, ceftazidime and ciprofloxacin on the expression of surface hydrophobicity and adherence to polyvinyl chloride, siliconized latex and polyurethane was evaluated. None of the antimicrobials significantly altered the expression of surface hydrophobicity. Subinhibitory concentrations of amikacin did not significantly reduce the adherence of P. aeruginosa to any of these 3 biomaterials. A significant inhibition of the adherence of polyvinyl chloride and siliconized latex but not to polyurethane was induced by both ceftazidime (p less than 0.05 to p less than 0.01 in different times) and ciprofloxacin (p less than 0.01). The effect of ceftazidime was present only for the first 4 h of bacteria-biomaterial interaction, whereas that of ciprofloxacin persisted throughout the study period (72 h).