Guideline 2010 for cardiopulmonary resuscitation was released the other day. There is no big change in the use of a defibrillator. Asynchronous defibrillation is used as a therapy for VF and pulseless VT. When you find a patient, start CPR immediately and prepare a defibrillator. About the value of energy, comply a recommended value of defibrillator's manufacturer with biphasic waveform, on the other hand, deliver 360J shock with monophasic waveform. Cardioversion is used as a therapy for supraventricular arrhythmia like atrial fibrillation. It is important to synchronize with QRS complex on ECG surely and deliver a shock. If it is not synchronized surely, there is a possibility to occur VF. Transcutaneous pacing is used as a therapy for bradycardia. It produces a depolarization of myocardium by giving current stimulus from a surface of a body, and force a heart to contract. It is usually carried out at demand mode, and confirmed that a heart contracts certainly. Defibrillator is an only device to terminate VF and pulseless VT and it is important to test defibrillator usually so that it can be used any time it is necessary.