Background: Urinary tract infection (UTI) is the most common human bacterial infection that affects different age groups and can occur anywhere in the urinary tract. In this article, we tried to assess the pathogenic and antibiotic susceptibility pattern of these pathogens in inpatients and outpatients of Imam Khomeini hospital of Ardabil. Materials and Methods: In this retrospective and descriptive cross-sectional study we evaluated list of all patients using hospital information system (HIS) software and the result of urinary culture and gender and type of admission were recorded. Obtained data from the study were studied using descriptive statistics. Results: In outpatients and inpatients E. coli was agent in 74 cases (59.6%) and 72 cases (53.7%) respectively. The highest levels of antibiotic sensitivity of E. coli in outpatient and inpatients were to drugs of nitrofurantoin (72.9-70.8) and amikacin (56.7-48.6). The highest rates of antibiotic resistance of E. coli in outpatients were to drugs of cotrimoxazole (35.1 percent), ampicillin (24.3 percent) and ciprofloxacin (24.1 percent) and in hospitalized patients were to drugs of ciprofloxacin (40.2 %), ampicillin (37.5 percent) and gentamicin (27.7 percent). Conclusion: E. coli is the main cause of urinary tract infection in inpatients and outpatients of Imam Khomeini hospital of Ardebil and the most effective antibiotics are nitrofurantoin and amikacin in empirical treatment for these patients.