An experience based on 1,211 patients has shown aspiration needle biopsy to be a valuable technique for diagnosing bronchogenic carcinoma and other localized intrathoracic lesions that are beyond the reach of the fiberoptic bronchoscope. In 896 patients with malignant intrathoracic neoplasm, the aspirate demonstrated malignant cells in 96%. A false cytological diagnosis of carcinoma occured in 2 patients, for a true positive rate of 99%. However, the true negative rate was only 87%. In 77% of 31 immunosuppressed patients, the causative agent of a focal infectious process was diagnosed. Pneumothorax was the only notable complication, occuring in 24% of patients, with 14% requiring chest tube drainage. The procedure is relatively simple and rapid, generally causes little patient discomfort, and can be performed in virtually any hospital.