This is a review of the variety of pulmonary histologic artifacts and incidental findings that may come to the attention of the surgical pathologist. In some cases, these may lead to an erroneous diagnosis; in others, they may obscure the diagnosis. The following groups of lesions are discussed: artifacts seen in biopsy and resection material, site-specific changes commonly encountered, incidental findings and structures seen in biopsy and resection material, and age-related changes. A short review of normal histology is included for perspective and a discussion of the abnormal biopsy that appears normal on first review is presented.