Of 20 consecutive episodes of ventilator-associated pneumonia due to Acinetobacter baumannii, 18 were preceded by tracheobronchial colonization with strains ofA. baumannii that had the same antibiotic susceptibility pattern. When the results of routine surveillance cultures of endotracheal aspirate samples were compared with the results of bronchoalveolar lavage fluid cultures performed for patients who developed late-onset ventilator-associated pneumonia, the sensitivity of the surveillance cultures was 90%, and the negative predictive value was 96%. The positive predictive value of surveillance cultures for identifying causative pathogens in cases of pneumonia due to A. baumannii was good.