False-negative results from transthoracic needle aspiration biopsy of malignant lung masses may occur if a central necrotic area is present and is the source of the biopsy material. The purpose of this study is to determine if the use of ultrasonic guidance can improve the sensitivity of lung needle biopsies in this circumstance. Sixty patients with malignant lung masses underwent ultrasonic examination in an 18-month period. In 14 cases, ultrasound showed that the mass had a large central necrotic area that was at least half the diameter of the tumor. Under ultrasonic guidance, needle biopsy specimens were taken from the central necrotic area and from the tumor wall in each case. Adequate biopsy specimens were obtained in all 14 patients. In all cases, the mural biopsy material was diagnostic for malignant tumor, while the biopsy specimen from the necrotic center was nondiagnostic in 10 of 14 patients. No complications occurred. We conclude that ultrasonically guided lung biopsy is a useful and safe tool to avoid false-negative needle biopsy specimens in malignant lung tumors with necrotic centers.