Twenty-six multidrug-resistant Pseudomonas aeruginosa isolates were exposed over time to 300 microg of gamma-linolenic acid or arachidonic acid per ml or to the combination of both acids at 150 microg/ml each with ceftazidime and amikacin with or without albumin to observe the in vitro interactions of the antibiotics. Antibiotics and albumin were applied at their levels found in serum. Synergy between acids and antibiotics was found against 13 isolates, and it was expressed after 5 h of growth in the presence of albumin. The results indicate that further application in experimental infection models is merited.