Extracorporeal membrane oxygenation (ECMO) is a modified form of cardiopulmonary bypass. Although early trials were plagued by severe bleeding and high rates of death, subsequent experience with neonates found good survival, and ECMO became an important tool in the care of critically ill infants with respiratory failure. Since the 1980s, expansion to other groups (children, patients with cardiac disease, etc) followed as experience was obtained. Today, there is a rapid growth of ECMO, especially in the adult population. To date, >73,000 patients receiving ECMO have been reported to the international Extracorporeal Life Support Organization registry. This rapid growth in the usage of ECMO has made it possible for it to be included in the management algorithm of certain disease processes, such as ARDS, cardiopulmonary arrest, and septic shock. Significant advances in technology have made it possible to support patients on ECMO for weeks or months with success. Reduction in sedative use and experience with "awake" patients has led to ambulatory and mobile ECMO. Changes in ventilator support while on ECMO, even to the point of extubation, are also occurring. This article will review briefly some of the literature related to criteria for severity of illness before ECMO and related to ECMO care and practice. Issues relating to the use of ECMO as a resuscitative tool in cardiac arrest as well as the controversial topic of volume and outcome will also be presented.