Electrophysiological studies of a patient with cephalic tetanus, manifested by trismus and unilateral facial palsy, revealed that the trismus resulted from strictly unilateral masseter spasm which stopped during sleep, a normal silent period in the involved masseter muscles, initially prolonged distal latency of the paretic orbicularis muscles, and abnormal continuous muscle activity in the paretic facial muscles which stopped during sleep and after facial nerve block. We conclulde that the facial paralysis was probably secondary to peripheral nerve dysfunction and the continuous muscle potentials represented enhanced activity of the nucleus. An intensity spectrum of the inhibitory defect in tetanus is postulated.