Background and Objective: Urinary tract infection (UTIs) is one of the most common diagnosed infectious diseases. In order to determine the spectrum of bacterial etiology and antibiotic resistance pattern of the uropathogens that cause community acquired UTI, a retrospective study was performed in Research Center of Reference laboratories of Iran on urine samples of referred patients during a 4 years period (from 2002 to 2006). Materials and Methods: During the study period, 4207 urine specimens were cultured. Cultures with a significant bacterial growth were selected and susceptibility testing was performed using disk diffusion method. Results: Outof 4207 urine specimens, 476 (11%) yielded positive culture. Escherichia coli (44.5 %) and Klebsiella pneumoniae (8.5%) were the most predominant isolated bacteria respectively. Escherichia coli revealed the highest susceptibility among oral antibiotics to nitrofurantoin (76%) and the highest rate of resistance to carbenicillin (94%) and ampicillin (89%) respectively. In total isolates, the highest level of susceptibility was for imipenem (99%) and among oral antibiotics for nitrofurantoin (70 %), and the highest level of resistance was for carbenicillin (89%) and ampicillin (84%). Conclusion: The results of this study revealed a considerable resistance to fluoroquinolones and co-trimoxazole and a high sensitivity to nitrofurantoin among isolated bacteria. We strongly recommend nitrofurantoin as the drug of choice for empiric therapy of UTI in our country.