Thoracoscopy has been proposed as the procedure of choice for the evaluation of focal, suspected malignant pulmonary lesions in children. One drawback with this approach, however, is the concern that intraparenchymal lesions may go undetected. We prospectively evaluated the ability of an endoscopic ultrasonic probe to detect intraparenchymal nodules. The handheld probe contains a piezoelectric ultrasound emitter and receiver that operates at 7.5 MHz. The axial resolution of the probe is 1.1 cm. Two different probe tips were used. One is a forward viewing tip and the other is angled at 45° relative to the axis of the probe shaft. Both probes image 90° sectors. Twelve thoracoscopies on nine patients were performed using the ultrasound probe. Of seven patients with confirmed metastatic disease, six had thoracoscopy converted to open thoracotomy to assure that no lesion had been missed. The probe was able to accurately assess surrounding bronchovascular structures and the presence and location of previously placed surgical clips. Although deep structures were readily visualized with the probe, lesions within 1.5 cm of the surface of the lung were poorly visualized. No complications occurred. This ultrasound system allows for the distinction of dense lesions from the surrounding pulmonary parenchyma except for those lying near the surface of the lung, which are usually easy to see directly. Furthermore, the images define the bronchovascular structures adjacent to the lesion. This device may enhance thoracoscopy by facilitating the detection of, and ability to resect, pulmonary intraparenchymal lesions.