These guidelines contain recommendations for basic life support (BLS) and advanced life support (ALS) for adult patients and are based on the best available resuscitation science. The Chain of Survival, introduced in Major Concepts, is now expanded to emphasize the important component of survivorship during recovery from cardiac arrest, requires coordinated efforts from medical professionals in a variety of disciplines and, in the case of OHCA, from lay rescuers, emergency dispatchers, and first responders. In addition, specific recommendations about the training of resuscitation providers are provided in “Part 6: Resuscitation Education Science,” and recommendations about systems of care are provided in “Part 7: Systems of Care.”