AIM:Analysis of biofilm forming ability of nosocomial Pseudomonas aeruginosa strains.MATERIALS AND METHODS:148 P. aeruginosa strains were used in the study. Reference strain P. aeruginosa 27853 was used as control. Biofilm forming was studied on the surface of96-well polystyrol plate.RESULTS:Most of the P.aeruginosa strains isolated both in intensive care (75.5%) and in other units (76.8%) of all the health care institutions were forming films, but ICU group displayed high film forming activity more frequently. The highest indexes of biofilm forming ability were detected in strains isolated from washouts of catheters, sputum and wound discharge. A high correlation between film forming and haemolytic activity for cultures isolated from wound discharge (r = 0.852, p < 0.05) and sputum (r = 0.816, p < 0.05) was detected.IIn the latte rgroup a correlation between film forming and phospholipase activity (r = 0.677, p < 0.05) was also observed. Film forming process was more intensive at 20 degrees C in all the groups. In most of the cases intensity of film forming by P. aeruginosa was independent of the presence of metabolites and of other bacterial taxa.CONCLUSION:High film forming activity provides competitiveness of strains, and probably can be one of the markers of nosocomial isolates.