BACKGROUND: Pneumonia is a frequent complication in patients undergoing mechanical ventilation. Quantitative culture of protected specimen brush(PSB) have shown satisfactory diagnostic accuracy for the diagnosis of ventilator-associated pneumonia. However PSB method is invasive, expensive, and require a bronchoscopic procedure. But endotracheal aspiration(EA) is simple and less expensive. The purpose of our study was to investigate the diagnosic value of EA quantitative cultures. METHOD: We studied 15 cases of ventilator-associated pneumonia(for >72h of mechanical ventilation) patients. Patients were divided into two diagnostic categories. Group I was the patients who were suspicious of clinical pneumonia, Group II was the patients for control. The obtained samples by EA and PSB were homogenized for quantitative culture with a calibrated loop method in all patients. RESULT: Using 103cfu/ml, 105cfu/ml as threshold in quantitative culture of PSB, EA respectively, we found that EA quantitative cultures represented a relatively sentive(70%) and relatively specific (60%) method to diagnose the ventilator-associated pneumonia. CONCLUSION: Although EA quantitative cultures are less specific than PSB for diagnosing ventilator-associated pneumonia. EA quantitative cultures correlated with PSB quantitative culture in patients with clinical pneumonia and may be used to treat these patients when bronchoscopic procedures are not available.