BACKGROUND Knowledge of antimicrobial resistance pattern in Escherichia coli, the predominant pathogen associated with urinary tract infection (UTI), is important as a guide in selecting empirical antimicrobial therapy. The aim of this study was to determine the antibiotic susceptibility patterns of E. coli strains isolated from adult outpatients with UTI, in Izmir, Turkey. METHODS This study was performed with isolates from outpatients with UTI, collected from 5 university and tertiary-care hospitals in Izmir, Turkey. Isolates were analyzed by standard methods and antimicrobial susceptibility testing was performed by Kirby-Bauer disc diffusion method. RESULTS A total of 4,534 E. coli strains (3,449 females and 1,085 males) were examined. Antibiotic resistance rates of the isolates for female and male, respectively: Ampicillin (61.8%, 78.7%), amoxicillin-clavulanic acid (36.6%, 59.1%), cefuroxime (22.5%, 41.3%), cefotaxime (18.2%, 35.8%), piperacillin-tazobactam (11.6%, 31.2%), amikacin (8.3%, 13.9%), gentamicin (24.9%, 40%), trimethoprim-sulfamethoxazole (42.1%, 57.3%), and ciprofloxacin/norfloxacin (42.1%, 63.3%). Extended spectrum beta-lactamase rate was found to be 18.3% and 26.1% for females and males, respectively. The isolates were significantly more resistant to all antibiotics in men than in females in this study (p<0.001). CONCLUSIONS The most important finding of our study is that a considerable proportion of the studied E. coli isolates were resistant to most antibiotics except amikacin. These data provide useful information for clinicians in determining the appropriate empirical antimicrobial regimen, and help authorities to formulate antibiotic prescription policies.