BACKGROUND: Early diagnosis and proper antibiotic treatment are very important in the management of ventilator-associated pneumonia (VAP) because of its high mortality. Bronchoscopy with a protected specimen brush (PSB) has been considered the standard method to isolate the causative organisms of VAP. However, this method burdens consumer economically to purchase a PSB. Another useful method for the diagnosis of VAP is quantitative cultures of aspirated specimens through bronchoscopic bronchoalveolar lavage (BAL), for which the infusion of more than 120 ml of saline has been recommended for adequate sampling of a pulmonary segment. But occasionally it leads to deterioration of the patient's condition. We studied the diagnostic efficacy of minibronchoalveolar lavage (miniBAL), which retrieves only 25 ml of BAL fluid, in the isolation of causative organisms of VAP. METHODS: We included 38 consecutive patients (41 cases) suspected of having VAP on the basis of clinical evidence, who had received antibiotics before the bronchoscopy. The two diagnostic techniques of PSB and miniBAL, which were performed one after another at the same pulmonary segment, were compared prospectively. The cut-off values for quantitative cultures to define causative bacteria of VAP were more than 10(3) colony-forming units (cfu)/ml for PSB and more than 10(4) cfu/ml for BAL. RESULTS: The amount of instilled normal saline required to retrieve 25 ml of BAL fluid was 93 +/- 32 ml (mean +/- SD). The detection rate of causative agents was 46.3% (19/41) with PSB and 43.9% (18/41) with miniBAL. The concordance rate of PSB and miniBAL in the bacterial culture was 85.4% (35/41). Although arterial blood oxygen saturation dropped significantly (p<0.05) during (92 +/- 10 %) and 10 min after (95 +/- 3 %) miniBAL compared with the baseline (97 +/- 3 %), all except 3 cases were within normal ranges. The significantly elevated heart rate during (125 +/- 24/min, p<0.05) miniBAL compared with the baseline (111 +/- 22/min) recovered again in 10 min after (111 +/- 26/min) miniBAL. Transient hypotension was developed during the procedure in two cases. The procedure was stopped in one case due to atrial flutter. CONCLUSION: MiniBAL is a safe and effective technique to detect the causative organisms of VAP.