Prolonged complete support of the circulation and of gas exchange can be achieved by extracorporeal membrane oxygenation (ECMO) in infants and children with potentially reversible, albeit life-threatening, disease. This allows lung rest or cardiac rest at times when dependence in those organs would be physiologically expensive. Although ECMO has no intrinsic healing powers, pediatric hearts and lungs exhibit tremendous recuperative power once the cycle of injury, inefficient performance, abuse, and secondary injury can be broken. Recent advances in technology, although impressive, do not explain the rapid growth of clinical interest in ECMO. Most recent progress in ECMO derives from refinement of clinical practices and the application of this technology to new patient populations. ECMO is not itself an experiment. It is the application of ECMO that is experimental.