The aim of this study was to detect the antibiotic resistance rates of extended spectrum beta-lactamase (ESBL) producing Escherichia coli and Klebsiella spp. strains isolated from urinary tract infections (UTIs) in Private Acibadem Hospital, Istanbul, Turkey. A total of 1100 E.coli and 356 Klebsiella spp. strains isolated from 17.028 urine cultures which were processed between October 2006 and August 2007 in the clinical laboratory, were included to the study. Identification of bacteria and antibiotic susceptibility tests were performed by Phoenix (Becton Dickinson, USA) automated system. Of E.coli strains 12% (n= 132) were found positive for ESBL, while this rate was 12% (n= 41) for Klebsiella spp. strains (38 K.pneumoniae, 3 K.oxytoca). The resistance rates of ESBL producing E.coli and Klebsiella spp. strains were found as follows respectively; 3% and 2.4% for amikacin, 3% and 85.4% for nitrofurantoin, 0% and 4.9% for fosfomycin, 5.3% and 100% for cefoxitin, 21.2% and 58.5% for piperacilin/tazobactam, 34.8% and 41.5% for gentamicin, 68.9% and 58% for trimethoprim/sulfamethoxazole (TMP-SMX), 75.9% and 56.1% for tobramycin, 80.3% and 21.9% for ciprofloxacin and norfloxacin. All of the ESBL positive E.coli and Klebsiella spp. strains were resistant to ampicilin, aztreonam, cefazolin, cefepime, ceftazidime, ceftriaxone and cefuroxime-sodium; while all of the ESBL positive E.coli and Klebsiella spp. strains were sensitive to imipenem and meropenem. The rates of resistance obtained in this study were higher than the rates obtained in other studies performed in our country. This could be attributed to the different antibiotic use policies of different centers or to more frequent use of antibiotics by the patients applied to private hospitals, owing to their higher socioeconomical status and easier attainment of antibiotics without prescription.