It has been studied the antibiotic sensitivity of 27 Pseudomonas aeruginosa strains belonging to only two types, isolated hospitalized children and responsible of different clinical pictures. The strains were in vitro resistant to Carbenicillin, Sisomicine, Gentamycine and many other antibiotic tested, partially resistant to Tobramycin and sensitive to Amikacine, Polimixine B and Colistatin.