Pseudomonas aeruginosa is associated with chronic and progressive lung disease and is closely related to increased morbidity and mortality in cystic fibrosis (CF) patients. Hypermutable (HPM) P. aeruginosa isolates have been described in these patients and are usually associated with antibiotic resistance. This study aimed to investigate the occurrence of carbapenem resistance and hypermutable phenotype in 179 P. aeruginosa isolates from 8 chronically CF patients assisted at two reference centers in Rio de Janeiro, Brazil. Using disk diffusion test, non-susceptible (NS) rates higher than 40% were observed for imipenem, amikacin, and gentamicin. A total of 79 isolates (44.1%), 71 (39.6%), and 8 (4.4%) were classified as carbapenem-resistant (CR resistance to at least one carbapenem), multidrug-resistant (MDR), and extensively drug-resistant (XDR), respectively. Minimal inhibitory concentration was determined for 79 CR P. aeruginosa and showed the following variations: 4 and 128 mu g/mL to imipenem, 4 and 64 mu g/mL to meropenem, and 4 and >= 32 mu g/mL to doripenem. We have found only four (2.23%) HPM isolates from 4 patients. Analyzing the genetic relationship among the HPM isolates, 3 pulsed-field gel electrophoresis/pulsotypes (D, M, and J) were observed. Only M pulsotype was recovered from two patients in different years. Polymerase chain reaction screening for bla(GES), bla(IMP), bla(KPC), bla(NDM), bla(OXA-48), bla(SPM), and bla(VIM) genes was performed for all CR isolates and none of them were positive. Our results demonstrate a high occurrence of CR and MDR P. aeruginosa of CF patients follow-up in both centers studied, while the presence of HPM is still unusual.