Background: Among the most common infectious diseases, second ranking after respiratory (tract) system infection is urinary tract infection which involve (infects) about 250 million people in developing countries annually. Objectives: The purpose of this study is to investigate the pattern of antibiotic resistance in common pathogens that cause urinary tract infection. This study is the first to evaluate the incidence of antibiotic resistance is the large number of samples in Iran. Patients and Methods: The susceptibility of samples obtained from 14,332 patients with urinary tract infections admitted to different medical diagnostic laboratories of Tehran, was measured using disk diffusion method for 18 common antibiotics. Results: Most of the identified bacteria were Escherichia coli (64.56%) and Klebsiella pneumoniae (13.78%). The most resistant antibiotics were respectively identified as trimethoprim/ sulfamethoxazole (61.35%) for E-coli and (49.6%) for Klebsiella sp. Also intermediate resistance to Nitrofurantion and Chlor tetracycline was observed. Conclusions: The findings of this study indicate that E. coli is the predominant pathogen of this infection. There are also bacteria with high resistance that Interfere with prescription of drugs in order to treat urinary tract system infection. Also increasing of resistance to antibiotics among bacterial pathogens is evolving and requires an inspectoral and research procedure which could provide more information for doctors to treat the infection more efficiently.