Rationale: Although the serial dilution technique for quantitative culture of bronchoalveolar fluid is considered to be the gold standard for the diagnosis of ventilator-associated pneumonia, it is more labor intensive than the calibrated loop technique. Objective: We sought to determine the agreement between the calibrated loop and serial dilution techniques in the diagnosis of ventilator-associated pneumonia. Methods: We prospectively measured bacterial colony counts by the serial dilution and calibrated loop techniques in 121 bronchoalveolar lavage samples of 104 patients with suspected ventilator-associated pneumonia. Measurements and Main Results: At the time of bronchoscopy, patients had received mechanical ventilation for a median of 8 days. Patients were receiving antibiotics when 90 of the 121 (74.4%) bronchoalveolar samples were obtained. The colony counts of 13 bacterial isolates were too numerous to count by the calibrated loop technique; by serial dilution technique, their counts ranged from 4.70 log10 to 6.74 log10 colony forming unit (CFU)/mL. Fifty other bacteria had paired colony counts measured by each of the two techniques: the bias (95% confidence interval) between the two techniques was -0.380 (-0.665 to -0.095) log10 CFU/mL with precision of 1.002 log10 CFU/mL and 95% limits of agreement -2.344 to 1.584 log10 CFU/mL. Using the threshold of 4 log10 CFU/mL as a criterion for the diagnosis of ventilator-associated pneumonia, there was discordance only for one bacterial organism between the two techniques. Conclusions: The calibrated loop technique can be used for the diagnosis of ventilator-associated pneumonia using bronchoalveolar fluid.