Both supraventricular and ventricular arrhythmias are associated with increased mortality and morbidity. Numerous antiarrhythmics have been developed in an attempt to decrease the frequency of these arrhythmias, hoping to improve survival and improve quality of life. Antiarrhythmic agents are a diverse group of drugs that affect various cardiac ionic channels and block specific arrhythmias. However, despite the suppression of these potentially lethal cardiac arrhythmias, only the β blockers have been shown to reduce sudden arrhythmic death, especially in patients with prior myocardial infarction or heart failure. Some antiarrhythmic agents can also worsen the index arrhythmia and caution must be used especially in the compromised patient. A simple guideline is as follows: For conversion of atrial fibrillation or flutter to sinus rhythm, in the absence of structural heart disease, intravenous ibutilide or oral propafenone or flecainide are good choices. For maintenance of sinus rhythm, propafenone or flecainide are logical choices. In the presence of structural heart disease, amiodarone, dofetilide, or dl sotalol are preferred. In heart failure, dofetilide or amiodarone are the logical choices. The role of antiarrhythmic therapy for ventricular arrhythmias is questionable and may be contraindicated, except for the use of β blockers. The implantable cardioverter-defibrillator is often used in patients at high risk. At times, the addition of an antiarrhythmic agent such as amiodarone may be justified.