In this study we aimed to assess the safety and efficacy of high-dose IV colistin (COL) and aerosolized COL for the treatment of Acinetobacter baumannii ventilator-associated pneumonia (VAP). Critically ill adult patients who received IV COL for multidrug-resistant A. baumannii VAP were evaluated retrospectively. A total of 45 patients were evaluated [15 patients with high-dose COL (2.5 mg/kg every 6 h), 20 patients with normal dose (2.5 mg/kg every 12 h), and 10 patients with low dose, determined according to creatine clearance]. Aerosolized COL was used in 29 patients treated with parenteral COL and 16 patients received only parenteral COL. The clinical response rates on the fifth day were 50, 30, and 27 % with the normal, low, and high doses, respectively. However, the clinical response rates at the end of the therapy had declined to 30, 30, and 7 % with the normal, low, and high doses, respectively. The bacteriological clearance rates at the end of the therapy were 65, 75, and 64 %, with the normal, low, and high doses, respectively. With the aerosolized COL, the clinical response rates on the fifth day and at the end of the therapy were 35 and 14 %, whereas these rates were 44 and 38 % without the aerosolized COL. Bacteriological clearance rates with and without the aerosolized COL were 76 and 69 %, respectively. The nephrotoxicity rate was 40 % for the high-dose COL, whereas it was 35 % for the normal dose, and 20 % for the low-dose COL. In conclusion, higher doses of COL and aerosolized COL had no advantages over lower doses in alleviating multidrug-resistant A. baumannii VAP. Moreover, the higher doses and the aerosolized COL increased the nephrotoxicity risk and seemed not to be safe.