Congenital lesion of the left facial nerve trunk has been investigated in a 30-year-old woman. Upon stimulation of the left facial nerve, no response was evoked in any of the mimic muscles. The patient was able to perform voluntary contractions of the left corrugator glabellae muscle and of the left corner of the orbicular oral muscle; these contractions were recorded electromyographically. The stimulation of the right facial nerve elicited responses in the referred left mimic muscles. This circumstance indicated their activity to be due to contralateral reinnervation by the intact facial nerve. The blink reflex examination evoked no response on the left side, while the blink reflex on the right side was elicited with both its components, both upon ipsi- and contralateral stimulation.