Bronchoalveolar lavage (BAL) is quite useful in the diagnosis of nonbacterial lung infections, especially in immunocompromised patients, and recent studies have suggested that BAL may be useful in the diagnosis of bacterial pneumonia as well. Because previous studies indicated that bronchoscopic aspirates are usually contaminated by oropharyngeal flora, we anticipated that BAL fluid would also likely be contaminated. Therefore, the purpose of this study was to perform quantitative bacterial cultures on BAL fluids obtained from eight normal subjects. Prior to each procedure, saline was aspirated through the bronchoscope and submitted for culture. A protected brush catheter (PBC) specimen was obtained from each subject's right middle lobe, and then a BAL specimen was obtained from the same location. All specimens were quantitatively cultured for aerobic and anaerobic organisms. In addition, lidocaine concentrations were measured in the BAL fluids and the PBC specimens. Six of the eight bronchoscope cultures were sterile. Seven of the eight PBC specimens were sterile and one yielded less than 10(3) cfu/ml of normal oropharyngeal flora. One BAL fluid specimen was sterile and seven yielded from one to four bacterial strains each; however, quantitation revealed less than 10(4) cfu/ml in all specimens. Lidocaine concentrations (mean +/- 1 SD) were as follows: PBC specimen, 0.81 microgram/ml (+/- 0.62); BAL fluid specimen, 62.6 micrograms/ml (+/- 43). We conclude that BAL fluid obtained from normal subjects is frequently contaminated by oropharyngeal bacterial flora.(ABSTRACT TRUNCATED AT 250 WORDS)