The authors summarize 5 years' experience with transthoracic fine-needle aspiration (TFNA) in 180 patients. Aspirated tumors tended to be large and peripheral. A large pneumothorax was seen after 4.3% of aspirations, and various minor complications followed another 23.3%. Emphysema was a significant risk factor for complications. Follow-up confirmed 151 cancers, with a wide variety of origins and histologic types. In the diagnosis of cancer, TFNA cytology had a specificity of 100% and a sensitivity of 82%. Positive TFNA findings usually provided the earliest microscopic diagnosis of cancer or of cancer stage.