A non-invasive method for the objective measurement of the functional state of the autonomic nervous system, including the balance between its two divisions, sympathetic and parasympathetic. The method is based on the iontophoretic application of different concentrations of the natural mediators noradrenaline and acetylcholine, and on the visual or instrumental assessment, based on color or conductivity measurement, of the concentrations causing vasoconstriction, and respectively, vasodilatation of the cutaneous vessels.