Heart failure is accompanied by major disturbances of the functioning of the sympathetic nervous system: global overactivation and local modifications of the adrenergic system. 123I-MIBG cardiac scintigraphy is an isotope technique investigating presynaptic adrenergic function. The cardiac uptake of MIBG is decreased during heart failure, reflecting a reduction of norepinephrine reuptake by cardiac presynaptic nerve endings. Alteration of presynaptic function occurs early and plays an important role in the pathogenesis of the deterioration of heart failure. 123I-MIBG cardiac scintigraphy allows in vivo assessment of the myocardial adrenergic reserves of patients with congestive heart failure. It should be proposed in all patients with severe ventricular dysfunction to help define the indications for heart transplantation.