Background: Recently ventilator-associated pneumonia (VAP) caused by multi-drug resistant (MDR) gram-negative bacteria has been increasing. Meanwhile the colistin is active against gram-negative bacteria, including the MDR pathogens such as Acinetobacter baumannii, and Pseudomonas aeruginosa, intravenous colistin was limited because of its nephrotoxicity and neurotoxicity. Furthermore the aerosolized colistin introduction preventing systemic adverse effects is controversy whether it is effective or not. We conducted the present study to assess the effectiveness and safety of aerosolized colistin for the treatment of pneumonia by MDR gram-negative pathogens. Methods: From February 2012 to September 2012 in medical intensive care unit of single tertiary academy hospital, retro-spectively medical records were reviewed in 11 patients who received inhaled colistin due to VAP by MDR pathogens. The favorable responses were defined as clinical and radiological improvements and/or negative conversion of cultures. Results: The average length of stay in the ICU was 26.9±9.4 days. The mean duration of aerosolized colistin therapy was 10.8±6.4 days. 7 patients of 11 patients showed favorable responses to the therapy (63.6%). Follow-up cultures were available for 8 patients, and the negative conversion was 4 cases (36.4%). 2 patients experienced adverse event related with nephrotoxicity (18.2%), and one was stopped because of bronchospasm (9.1%). Conclusions: Aerosolized colistin appears to be relatively safe and effective option for the treatment of respiratory tract infection.