All computed tomography directed lung biopsies from 1987 to 1991 were retrospectively reviewed. Pneumothorax occurred in 33 of 93 (35 percent) patients; 16 of these patients or 17 percent overall required a chest tube. No correlation was found between the presence of obstructive lung disease and the incidence of pneumothorax. Patients with smaller lesions were more likely to incur a pneumothorax. No relation was found with central or peripheral location, patient's age, or the operator and the incidence of pneumothorax. Patients with a pneumothorax were more likely to require a chest tube if they had obstructive lung disease.