The various techniques available for determining endotracheal tube position after intubation of a newborn are auscultation of the chest, observation of distance rings on the endotracheal tube, and chest radiology. Radiology is considered to be the most reliable method. We evaluated the use of a new ultra-thin fiberoptic bronchoscope on 20 recently intubated newborn infants to determine the position of the endotracheal tube and compared the technique with radiology. The accuracy of the two methods was comparable (correlation 0.91, P less than 0.001). Adverse changes in transcutaneous PO2 were observed during both procedures but were more marked during radiology than bronchoscopy. We conclude that the bronchoscopic technique of determining endotracheal tube position is both as safe and as accurate as radiologic technique.