Percutaneous needle biopsy (PNB) of localized thoracic disease has become a widespread procedure in many institutions. The development of special small caliber needles has increased the diagnostic yield of PNB partly by increasing the amount of tissue from biopsy, often enabling histologic examination. Nevertheless, in a significant number of patients only cytopathologic examination is possible on the retrieved biopsy fragments, necessitating the presence of a trained cytopathologist in the biopsy room. Furthermore multiple biopsy needle passages often are required, increasing the risk for complications such as pneumothorax. We have evaluated the use of a small-caliber tissue biopsy cutting needle, consistently yielding sufficient biopsy tissue for histologic examination. In 25 pleural and mediastinal lesions, which could be biopsied without passage through aerated lung, there was a 93% sensitivity (7% false-negative results) for neoplasm and a 100% accuracy for benign disease. There were no complications. In 32 patients with lesions of 1 cm in diameter or more surrounded with aerated lung tissue, adequate histologic examination was feasible on every biopsy specimen after only one needle passage. There was an 87% sensitivity of PNB in neoplastic disease (13% false-negatives). In the patients with benign disease, there was a 100% accuracy. There was a 15.6% risk for pneumothorax. In only one patient (3%), however, was chest drainage necessary. One patient (3%) had mild hemoptysis. We conclude that percutaneous biopsy of localized pulmonary, pleural, and mediastinal lesions with a new small-caliber automatic guillotine cutting needle is safe and efficient, enabling recovery of sufficient tissue for histologic examination with a single-pass procedure, thus minimizing the risk for pneumothorax, eliminating the need for a cytopathologist in the biopsy room, and shortening the duration of the procedure.