Use of fiberoptic bronchoscopy to acquire pulmonary secretions has been shown to yield unreliable bacterial cultures. However, microscopic examination of such material has received little attention. In this study, 69 bronchoscopies were evaluated. Clinical assessment of the presence of a lower respiratory tract infection was made and cultures obtained. In addition, each specimen was analyzed with a Gram-stained smear. The Gram-stained smears of these specimens correlated extremely well with the clinical assessment. In 67 of the 69 cases, bronchoscopy yielded material whose Gram-stained smear accurately reflected the presence or absence of a pyogenic infection. In patients with lower respiratory tract infections, the smear also predicted the likely category of the causative organism. This study suggests that microscopic examination of lower respiratory tract secretions helps make fiberoptic bronchoscopy a potentially useful alternative in the evaluation of bacterial lung infections.