We examined the frequency of isolation and the antimicrobial resistance of Burkholderia cepacia complex, Stenotrophomonas maltophilia and Achromobacter xylosoxidans in cystic fibrosis patients from 2000 to 2004. Strains susceptibility to tobramycin, piperacillin/tazobactam, imipenem, gentamicin, ciprofloxacin and ceftazidime was determined by disc diffusion assay. B. cepacia complex showed a very high resistance also to ciprofloxacin reaching 100% in 2004. S. maltophilia and A. xvylosoxidans showed high rates of antimicrobial resistance both aminoglycoside and ciprofloxacin. It is very important to monitor the percentage of isolation of these species over time to verify strains resistance to antibiotics and also to test new combinations of antimicrobial agents.