The decision to treat arrhythmias can be based upon subjective symptoms or on the potential danger of the particular rhythm disturbance. The underlying myocardial condition has also to be considered. The main practical problem is to define which premature ventricular beats (PVB) require treatment in the hope of reducing the risk of sudden death. At the moment the answer can be given only for treatment of PVB's with beta-blockers in patients who have had myocardial infarction; the risk of sudden death is diminished in these cases. One may extend this approach to other cardiopathies or to other antiarrhythmic drugs, but thus far this has not been proven to be effective.