The evolution of the human in caring for others is reflected in the development of cardiopulmonary resuscitation (CPR). Superstition, divine intervention and finally science have contributed to the development of a technique which may allow any person to save anothers life. Fully 50% of the first presentation of coronary artery disease is sudden death, typically in (western) men. [Anonymous, 2000, ID-469] However, achieving a clear understanding of why CPR saves some lives remains shrouded in mist; mist made even thicker by contradictory reports, different school of thought and persistently low survival rates. Despite the suggestion that much remains unclear, CPR is not new. An early report, in an 18 year old woman, of CPR as performed today, initially known as closed-chest cardiac resuscitation (CCCR), dates from 1858 [Husveti, ID-649]. Following airway obstruction and hypoxia, cardiac arrest occurred. Artificial respiration and compressions on the anterior chest wall for six minutes resolved the incident successfully. Surprisingly little seems to have changed in CCCR since that early report. Even though CPR has been researched extensively, the number of survivors remains disappointingly small. Survival rates as low as a few percent and extending upwards to 30%, (most frequently ±10%) survival for out-of-hospital resuscitation have been reported, without a clear understanding of why some patients do and others do not survive when given the same care. CPR is a technique taught to tens of thousands each year. This chapter will address functional aspects of CPR required for a working understanding of the biomedical aspects of CPR. It does not purport to be a CPR course, although practical aspects relevant to understanding will be addressed, but not exhaustively. The development in CPR and the contributions of science to this development will be presented, with emphasis on the cardiovascular system and only on the artificial respiratory aspects when needed. Schools of thought, chronologically organized, with the effects of physical and experimental models on their development and validity will allow the reader to analyze strengths and weaknesses.