Electroneuronography (ENoG) involves the recording of a summation potential of motor units provoked by an appropriate electrical stimulus. Degeneration (and obviously interruption) of a nerve fibre always means the denervation of all muscular fibres related to them. So the diminution in summation potential amplitude will be proportional to the number of denervated motor units. The test is based on a comparison of responses to stimuli of equal intensity between healthy and diseased side. Comparison with the unimpaired side, makes it possible to establish the percentage number of nerve fibres on the damaged side capable of provoking a contraction in the muscular fibres to which they are distributed. The results obtained in 60 personal cases are illustrated and the undeniable advantages offered by this straightforward diagnostic method discussed with respect to evaluating the development of facial nerve paralysis and the precise, early establishment of therapeutic indications, particularly where surgery is necessary.