Magnesium deficit and other electrolyte abnormalities is a frequent disorder in patients with congestive heart failure. Overstimulation of the renin-angiotensin-aldosterone system, long-term administration of diuretics, digoxin, poor oral intake and impaired absorption contribute to these electrolytes abnormalities. Hypomagnesaemia and depletion of intracellular magnesium stores have been held responsible for a variety of cardiovascular and other functional abnormalities, including various arrhythmias, impairment of cardiac contractility, and vasoconstriction. Because sudden death is prevalent in congestive heart failure, a causal relationship between arrhythmias and magnesium deficiency has been proposed. Reportedly, administration of magnesium can suppress ventricular arrhythmias;however, it remains to be elucidated whether administration of magnesium prevents sudden death and improves prognosis of the patients with congestive heart failure. Nevertheless, since magnesium depletion may be prevalent in congestive heart failure and magnesium has anti-arrhythmic and beneficial cardiovascular effects, magnesium should be supplemented to the patients suspected to have its deficiency.