Automatic implantable cardioverter defibrillator(AICD) is a device that senses ventricular tarchycardia and ventricular fibrillation and responses with counter-shocks to the heart. We experienced a case of AICD implantation to prevent sudden cardiac death. A-22-year-old male was operated under O2, N2o, fentanyl, low dose enflurane anesthesia. The diagnosis was familial long QT syndrome. Lead was introduced to the right ventricular apex through left subclavian vein and generator was placed between pectoralis muscles. Then defibrillation threshold testing was performed. Ventricular fibrillation was induced with Twave shock of 3 joule and defibrillation with 5 joule terminated ventricular fibrillation successfully. After ventricular fibrillation, his blood pressure decreased to 30mmHg. When ventricular fibrillation was converted to normal rhythm, it retured to normal range. After operation, patient was transferred to the ICU and stayed there for 3 days.