Findings in patients who underwent computed tomography (CT)-guided percutaneous needle biopsy (n = 131) of lung are described. In those in whom the needle traversed aerated lung, complications developed in 51% (40 of 79). The rate of pneumothorax was 46% (36 of 79). In those in whom the needle did not traverse aerated lung (n = 52), minor hemoptysis in one patient (2%) was the only complication (P less than .0001). When a percutaneous CT-guided lung biopsy needle does not traverse aerated lung, the likelihood of complication appears to be slight.