A case is presented in which amiodarone was administered to suppress paroxysmal atrial fibrillation in a patient with an idiopathic cardiomyopathy. Eleven days after initiation of therapy with amiodarone, the patient experienced syncope and was noted to have recurrent episodes of polymorphous ventricular tachycardia. The patient was hospitalized and treated with a bolus as well as continuous infusion of intravenous magnesium sulfate. When the infusion was transiently discontinued, recurrences of polymorphous ventricular tachycardia were noted. The probable proarrhythmic action of amiodarone, although rare, is reviewed along with a discussion of the novel use of intravenous magnesium sulfate therapy.