The purpose of this study was to determine the agents of urinary tract infections and their susceptibility to antibiotics. The potency and spectrum of various antimicrobial agents tested against 8692 bacterial isolates causing urinary tract infection in hospitalized and out-patients in the authors' hospital between 1999 and 2002 were studied. The most prevalent aetiological agent was Escherichia coli (51.5%), followed by Klebsiella pneumoniae (11%), and Enterococcus faecalis (6.2%). Disk diffusion test and Sceptor Identification System were used for determining antibiotic susceptibility. For E. coli the antibiotic susceptibilities were: to ceftriakson 92.6%, gentamicin 90.2%, ciprofloxacin 82.5%, co-trimoxazol 47.4% in outpatients. For E. coli strains meropenem (98.9%), imipenem (96.4%), cefepime (95.7%), amikacin (94.6%), ceftriaxone (87%), for K. pneumoniae meropenem (97.8%), imipenem (96%), amikacin (80.7%); for Acinetobacter baumannii meropenem (85.8%) and imipenem (81%) were found to be the most effective antimicrobials in hospitalized patients. Knowing the distribution of the strains and differences in antibiotic resistance profiles in clinical patients and outpatients will be a guide for the selection of relevant antibiotics until culture and antibiotic susceptibilty tests are resulted.