Eleven patients who had lung tumors associated with obstructive pneumonitis and who failed to yield diagnostic material at conventional bronchoscopic biopsy underwent real-time ultrasonographic (US) studies and US-guided aspiration biopsy. Sonography of the consolidated lung showed a wedge-shaped hypoechoic lesion containing a fluid bronchogram. The presumed obstructing tumor was seen as a hypoechoic nodule near the hilum or as a well-defined hyperechoic mass inside the partially consolidated lung. Computed tomography (CT) was superior to US in demonstrating the bronchial obstruction (P less than .05). However, there were no significant differences between CT and US in demonstrating the obstructing tumor (P greater than .10). In all 11 patients the diagnosis was made by means of US-guided transthoracic aspiration biopsy and in eight patients also by means of Trucut biopsy. No complications were observed in the studies. It is concluded that US and US-guided aspiration biopsy are useful adjunct diagnostic techniques for lung tumor patients with obstructive pneumonitis.