Since the lungs of neonates should be sterile after birth, we investigated the ability of tracheal aspiration to provide early diagnosis of congenital pneumonias. Forty infants presenting with respiratory symptoms and positive chest radiographs by eight hours of age were assigned to control or suspect groups based on the presence of bacteria after sputum analysis. These groups showed no difference in maternal age, parity, duration of membrane rupture or labor, Apgar scores, or birth weight and gestational age. Polymorphonuclear leukocytes (PMNS) were found in 7 of 20 control and 16 of 20 suspect infants. Positive blood cultures were obtained in 1 of 20 control and 14 of 20 infants suspect for pneumonia. Tracheal isolates included Group B streptococci (11), Hemophilus influenzae (2), Escherichia coli (2), Listeria monocytogenes (2), alpha hemolytic streptococci (2), and Staphylococcus aureus (1) in the suspect neonates, and Group B streptococcus from the single control infant. At the time of tracheal aspiration, no statistical differences could be ascertained between the groups regarding pulse, respirations, blood pressure, rectal temperature, pH and base deficit, and corrected absolute numbers of segmented and immature PMNS. The presence of bacteria on histologic analysis of sputum obtained by tracheal aspirate, and the subsequent isolation of a similar bacterium in blood and sputum, provides a valuable tool in the diagnosis of congenital pneumonia when compared to other clinical variables.