Forty-six patients with peripheral lung lesions underwent ultrasound-guided percutaneous needle aspiration biopsy. Aspirates were sent for cytological and/or microbiological examination. Confirmative diagnosis was obtained in 40 patients (86.9%). Twenty-eight patients had positive cytology for malignancy and 12 patients with benign lesions had diagnosis made by cytologic and microbiologic examination. None of the lesions could be diagnosed by sputum cytology and fibreoptic bronchoscopy with biopsy or brushings. No complication was observed in any patient. We conclude that ultrasound guided aspiration biopsy is a useful and safe method for the diagnosis of peripheral pulmonary masses. The diagnostic yield far exceeds that which can be obtained by sputum cytology and fibreoptic bronchoscopy with biopsy.