Mechanical systems to oxygenate blood outside of the body were first employed in clinical medicine as a component of the "heart-lung machine". The artificial lung has been an essential component of the technology underlying the progress of cardiovascular surgery since 1950. Its impact on clinical medicine can be measured by the widespread acceptance of cardiac surgery for the treatment first of congenital malformations, then valvular lesions, and more recently, coronary artery disease. Whereas the use of the artificial lung during temporary exclusion of the pulmonary circulation for surgical purposes is now well established, the chronic application of extracorporeal membrane oxygenation and end-stage resporatory failure is still controversial. Internally implantable lung prostheses are still at the conceptual or developmental stage, and are unlikely to impact on clinical medicine for another decade.