The efficacy of magnesium therapy in patients with ventricular tachycardia has previously been reported. Recently completed and ongoing studies validate earlier observations that potassium and magnesium supplementation may control other cardiac arrhythmias, particularly in hypomagnesemic patients. Magnesium treatment is a viable therapeutic option when other antiarrhythmic agents fail to suppress ventricular tachycardia, ventricular fibrillation, multifocal atrial tachycardia, atrial fibrillation and supraventricular tachycardia.