The advent of cardiopulmonary bypass in 1953, and its subsequent continuous refinements, have securely established the specialty of cardiovascular surgery. In conjunction with the improved methods of myocardial preservation, this has allowed the safe repair of acquired and complex congenital cardiac defects. During the years, the many variables of the systems used for cardiopulmonary bypass have been altered to the point that most operations are now reproducible with, relatively, low morbidity and mortality. Although in its present form the system is quite reasonable for most routine surgery, it is far from perfect. There remains, therefore, a quest for alterations to improve the system as an ongoing process. Certain complications of open-heart surgery persist and many new and unique approaches to the concept of organ protection and the treatment of these complications must be developed and refined.