The parietal and visceral pleura are specialized membranes which are highly efficient in keeping the pleural space essentially dry and free of protein and particulate matter. Radiology has played a pivotal role in the understanding of pleural diseases because radiography and, more recently, computed tomography (CT), sonography, and magnetic resonance imaging (MRI) have allowed in vivo visualization of abnormalities. In addition, these newer modalities have been invaluable in guiding diagnostic and therapeutic measures. Cross-sectional imaging techniques, particularly CT, are frequently of assistance in determining whether tube thoracostomy or other surgical measures are indicated, and when these procedures should be performed. The application of newer imaging modalities in expediting the management of pleural diseases is emphasized. The anatomy, histology, and physiology of the pleura, in both normal and disease states, are also reviewed.