The ERC Guidelines 2005 regarding the resuscitation of children and neonates recommend changes in treatment algorithms. Cardiac arrest in children is most often caused or worsened by hypoxic conditions. On confirmation of cardiac arrest in a child, treatment is initiated with 5 ventilations and continued with alternating cycles of 15 chest compressions and 2 ventilations. Defibrillation of ventricular fibrillation or pulseless ventricular tachycardia is given as single 4 J per kg(-1) shock in every cycle. Rhythm or pulse is not assessed immediately after defibrillation, but first after two minutes of basic life support, i.e. before a new attempt of defibrillation.