This article provides a comprehensive account of the anatomy and physiology of the intercostal space, the knowledge of which is important for thoracic surgeons. A wide variety of clinical applications involve the intercostal space, ranging from simple inspection of a widened space in the emphysematous patient, to thoracentesis, to the surgical preparation of an intercostal musculopleural flap. Each of these procedures can be easier and safer if the intercostal anatomy is thoroughly understood. The precise knowledge of the relationships between the neuromuscular and osseous components within the intercostal space may help reduce pain and improve chest wall motility.