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Abstract Background and Objective: Bacterial colonization in upper respiratory airways is one of the major risk factors for the development of the ventilator–associated pneumonia (VAP), which is the most common and serious hospital-acquired infection in intensive care unit (ICU). The aim of this study was to determine the frequency of oropharyngeal microorganisms of patients with tracheal tube hospitalized in ICU. Material and Methods: Of 39 patients hospitalized in ICU of panje Azar Hospital, the oropharyngeal cultures were taken after admission. The samples were evaluated for growth of Staphylococcus aureus, Pneumococcus, Enterococcus, Pseudomonas, and E-coli. Results: The mean age of the patients (21 men, 18 women) was 43.64±15.01. The culture was positive in 28.2% and the most common isolate was Pseudomonas aeruginosa (10.3%). Conclusion: Pseudomonas, which is the main pathogen for ventilator- associated pneumonia, may be a potential threat for the patients hospitalized in intensive care units. Keywords: Microbial Colonization, Endotracheal Tube, Intensive Care Unit, Ventilator Associated Pneumonia