The onset of serious arrhythmias during potassium depletion occurs rather frequently in female subjects who have undergone hypotensive-diuretic treatment, independently from the duration and doses of drugs. These arrhythmias which produce a cardiac arrest, can also occur in subjects not affected with heart disease. They are not necessarily preceeded by clinical prodrumus or other types of minor arrhythmias not accompanied by other important electrocardiographic or serum-logical alterations of hypokaliemia. The most commonly observed type is the "torsades de pointe", though cases of ventricular tachycardia or ventricular fibrillation are also documented. The ethiopathogenesis is discussed with regard to the alterations of the basic electrocardiogram as well as to the kind of major arrhythmia. In most cases , lidocaine has given the most satisfactory thmias, results in the treatment of these arrhythmias, probably because of the modality of the action which is substantially different from the other antiarrhythmic drugs.