The primary complication of transthoracic needle aspiration is pneumothorax. The efficacy and safety of using a small chest tube to treat this complication were examined by reviewing the records of 876 patients who underwent transthoracic needle aspirations between January 1981 and February 1986. Among these patients, 212 (24%) sustained a pneumothorax, and 92 (11%) required placement of a small 9-French chest tube attached to a flutter-type (Heimlich) valve. Duration of chest-tube drainage ranged between 24 hr and 3 weeks (mean, 2.2 days). Complete resolution of the pneumothorax and subsequent removal of the chest tube after 24 hr of drainage occurred in 38 (41%) of the 92 patients. Twenty-nine (32%) required 48 hr of drainage, and nine (10%) required 3 days. The remaining 16 (17%) required longer periods of drainage ranging from 4 days to 3 weeks. The tubes of six of this last group of patients were attached to a suction apparatus, and three of these patients eventually had a 28-French chest tube placed surgically. No significant complications occurred. The use of a small chest tube for treatment of pneumothorax after transthoracic needle aspiration is easy, safe, and efficacious.