Transthoracic needle aspiration is a relatively innocuous procedure used extensively in the diagnosis of pulmonary disease. Although its sensitivity for malignancy is high, a negative (benign) diagnosis is obtained in 5% to 25% of all cases. Some of these aspirates represent the result of inadequate sampling of a malignant tumor; others, however, are derived from a truly benign process. This review briefly describes and illustrates the cytologic features of these latter aspirates in order to exemplify the wide range of benign diseases that can be identified or suspected by transthoracic needle aspiration. Familiarity with such features should help the interpreting pathologist to prevent needless respiration or thoracotomy in many patients.