Out of 500 consecutive cases of Bell's aplsy 350 were subjected to clinical and electrical assessment to find early prognostic criteria. Clinical evaluation was carried out according to a scheme described. Electrical tests included nerve excitability, nerve conduction latency, muscle excitability, and needle electromyography. All were repeated at regular intervals. Analysis of the results showed that the presence or absence of voluntary function when the patient first presented gives no useful prognostication. The degree and time of recovery were related to the presence of nerve degeneration. This could be detected early by electrical testing. Nerve conduction latency has certain advantages over nerve stimulation. Electromyography was of some help in selecting incomplete degenerative lesions, and in the detection of early signs of recovery.