en Infectious diseases and public health Infectious diseases and public health Original article Original article <strong>Introduction: </strong><em>Acinetobacter baumannii</em> is one of the major causes of nosocomial infections. We investigated the distribution of <em>A. baumannii</em> among patients and the environment in special care units of a hospital in Tehran, Iran.<strong> Methods: </strong>Sixty-nine non-duplicate clinical and environmental samples were collected from ICU, Post-ICU, and CCU in EbneSina Hospital (Tehran, Iran) from June 2015 to April 2016. The isolates were identified using standard biochemical tests, and their identity was confirmed by detection of <em>bla</em>_oxa51gene. Susceptibility to 14 antibiotics was determined by disc the diffusion method, and genetic fingerprinting of the isolates was performed by random amplified polymorphic DNA (RAPD-PCR). <strong>Results: </strong>We recovered 66 <em>A.</em> <em>baumannii</em> isolates, 41 from patients, and 25 from the environment. All isolates from patients were resistant to all tested antibiotics except colistin. Environmental isolates were resistant to piperacillin (100%), tetracycline, piperacillin/tazobactam, beta-lactams and quinolones (86%), and amikacin (81%) but sensitive to colistin. The RAPD-PCR results revealed 35 clusters with 80% similarity. Despite the heterogeneity among the RAPD-PCR profiles, similar patterns were observed among 11 clusters comprising both clinical and environmental isolates. <strong>Conclusion: </strong>The results of this research suggest that the presence of <em>A.</em> <em>baumannii</em> on environmental surfaces could have played an essential role in the colonization of the hospitalized patients. Acinetobacter baumannii, RAPD-PCR, MDR, ICU, environmental contamination. 37 42 http://jommid.pasteur.ac.ir/browse.php?a_code=A-10-176-1&slc_lang=en&sid=1 Fereshteh Eftekhar f-eftekhar@sbu.ac.ir 0000-0002-2441-2582 Yes Shahid Beheshti University Nasrin Esmaeeli Torkanpoory nasrin.esmaeilee@gmail.com 0000-0002-0060-2189 No EbneSina Hospital, Tehran, Iran