Acinetobacter baumannii can survive for prolonged periods in unsuitable environmental conditions and easily spre-ad to patients in the hospital settings leading to healthcare-associated infections. Major risk factors for A.baumannii infections are mechanical ventilation, invasive procedures such as central venous catheter or urinary catheter and the use of broad-spectrum antibiotics. The mortality rates of nosocomial A.baumannii infections have been reported between 50-60%, changing due to several factors. The aim of this study was to investigate the factors associated with mortality in intensive care unit (ICU) patients diagnosed as nosocomial A.baumannii infections. The demographical, clinical and microbiological data of the patients who were followed in ICUs between September 2008 to March 2010 were evaluated retrospectively, and analyzed regarding the factors related to mortality. Blood, urine and tracheal aspirate samples were collected from suspected patients and cultivated on conventional agar media. The identification of the isolates and antibiotic susceptibilities were performed by using VITEK-2 (bioMerieux, USA) automated system. The patients with A.baumannii infections were grouped as died and survived cases, and the groups were compared according to following factors: age, gender, isolation day of bacteria in intensive care unit, type of clinical sample, implementation day of the central venous catheter, implementation of tracheotomy and/or intubation, operation, presence of diabetes mellitus, antibiotic use, day of hospitalization, day of mechanical ventilation and APACHE (Acute Physiology and Chronic Health Evaluation)-II score. A.baumannii infection was identified in 56 patients (29 female, 27 male; mean age: 63 years) in the intensive care units during the study period, and the total mortality rate was estimated as 77% (43/56). The implementation of intubation, mechanical ventilation, high APACHE II score and recovery of bacteria from respiratory tract were found statistically significant for A.baumannii infections related mortality (p< 0.05 for each parameter). Our data showed that Acinetobacter infection in the respiratory tract, implementation of intubation, mechanical ventilation and high APACHE II scores were the major risk factors related to mortality.