ABSTRACT Our purpose is to investigate the electrophysiological characteristics of Bell's palsy and to obtain clues for estimating prognosis in the late period by using electroneurography (ENoG). Thirty patients were followed by ENoG over a period of three months. They were evaluated through the forty full score system and classified into three groups according to the degrees of facial nerve recovery. There were significant differences between ENoG results of each group in the time course between 1.5 and 3.0 months of onset. The effect of increasing intensity on the amplitude is the most valid parameter for follow-up prognostic estimation. We concluded that the amount of non-degenerated synchronous firming fibers can allow us to estimate prognosis of Bell's palsy, if we make serial tests.