Objective: Multidrug resistance is a major problem of Pseudomonas aeruginosa strains. We aimed to determine the level of resistance to the antipseudomonal antibiotics, the change in the rates of antibiotic resistance over the years, and mortality rate during hospital stay. Methods: The microbiology database of P. aeruginosa isolated from 3708 sputum and 485 bronchial lavage samples at Chest Diseases Public Hospital from January 2009 to December 2013 was retrospectively reviewed. Imipenem, amikacin, tobramycin, ciprofloxacin, piperacillin, piperacillin/tazobactam ceftazidime, and cefepime resistance rates of P. aeruginosa strains were determined. Antimicrobial susceptibility was determined by the disk diffusion method, according to the Clinical Laboratory Standards Institute (CLSI) guidelines. P. aeruginosa was defined as resistant (resistance to at least one of the antipseudomonal antibiotics), and multidrug resistant (MDR) (resistance to three or more drugs of following classes: ?-lactam, carbapenem, aminoglycoside, and fluoroquinolone). Results: Five hundred and five P. aeruginosa isolates were tested. The antibiotic resistance rates were as follows; cefepime (26.7%), ceftazidime (23.2%), piperacillin (22.2%), imipenem (21.8%), piperacillin/tazobactam (19.2%), ciprofloxacin (17.4%), tobramycin (11.9%), and amikacin (7.3%). When compared 2009 and 2013, statistically significant reduction was observed in resistance rates to ciprofloxacin, amikacin, and cefepime antibiotics. Among 505 strains, 12.1% were designated as being MDR. Out of 505 patients investigated, 34 (6.7%) died during the hospital stay. Conclusion: The clinical significance of these findings is important in the selection of appropriate empirical treatment of serious P. aeruginosa infections.