In 46 consecutive patients undergoing transcutaneous needle aspiration of the lung, we evaluated the number of passes required to reliably predict the presence of malignancy. A diagnosis of malignancy was made in 38 of the 46 patients (84%), none of whom required more than 6 separate aspirations for a positive cytologic diagnosis to be made. The remaining 8 patients with a nonmalignant cytologic diagnosis on 6 separate aspirations were subsequently shown to have a benign lesion, either by surgical excision (5 patients), fiberoptic bronchoscopy (2 patients), or clinical follow-up (1 patient). Pneumothorax occurred in 12 of 46 patients (26%). We confirm that TCNA is a safe and reliable procedure in the valuation of lung masses and that, when adequate cellular material is obtained, 6 separate aspirations reliably predict the presence of malignancy.