In artificial pseudomonas infections undertaken on white mice the effectiveness of the aminoglycosides (gentamicin, tobramycin, netilmicin, amikacin) was compared. The most effective drugs on highly susceptible Ps. aeruginosa were amikacin and netilmicin. Moreover amikacin is probably capable of inhibiting pseudomonas toxin production. Therefore this preparation should be left in reserve for the treatment of serious pseudomonas processes.