This chapter explains the fundamental elements of resuscitation. Patients in cardiorespiratory arrest require prompt and effective resuscitation to improve chances of a good outcome. Identification of the underlying cardiac rhythm and treatment of any reversible causes is critical to achieve patient survival. A structured ABCDE approach and the ALS algorithm are commonly adopted to optimise patient assessment and management. An awareness of both technical and non-technical skills are important when dealing with the acutely deteriorating patient.