Nowadays, due to widespread use of broad range spectrum antibiotics in treatments, Pseudomonas aerugi- nosa developed high levels of resistance to these antibiotics. Therefore it is challenging to treat the infec- tions caused by P. aeruginosa. In this study, multi-drug resistant strains and antibiotype groups were identified by investigating resistance in P. aeruginosa strains isolated from three different hospitals in Ankara, against beta-lactam, aminoglycoside and ciprofloxacin. Thus, it was aimed that the most effective antibiotics for treat- ment of P. aeruginosa sourced infections were determined. Sixty-nine P. aeruginosa strains were investigated for resistance against aztreonam, meropenem, imipenem, amikacin, tobramycin, piperacillin, ceftazidime, ce- fepime and ciprofloxacin. It was found that the highest resistance rate was against aztreonam (66.6%) and the most effective antibiotic was found to be amikacin (5.7%). Additionally, the rate of multi-drug resistance in P. aeruginosa strains was determined as 36%. Although, 18 antibiotype groups were identified in P. aeruginosa strains, the highest antibiotype rate was observed in antibiotype 8 which was intermediate to aztronem and sensitive to other 8 antibiotics. In this respect, the combined treatment of aminoglycoside and ciprofloxacin is thought to be effective against resistant P.aeruginosa strains.