This study was designed to decide the most optimal sites of the active electrode in nerve conduction study of each branch of facial nerve. Twenty healthy male and female volunteers in 3rd and 4th decade were investigated. Our criteria for optimal sites of the active electrode were: i) intial negative take-off of the response, ii) maximal amplitude of the response, and iii) the most synchronized response,

The obtained optimal sites are as follows:

1) Frontalis (temporal branch): a point midway between the hair-line and the eyebrow along a line passing vertically through the pupil gazing the front.

2) Orbicularis oculi (zygomatic branch): a medial quarter between medial and lateral canthus.

3) Nasalis (buccal branch): muscle belly.

4) Triangularis (mandibular branch): 15 mm lateral to, and 30 mm below the corner of the mouth.

5) Orbicularis oris (zygomatic, mandibular, buccal branch): 2 mm below the lower lip midway between the midline and the corner of the mouth

Keywords :Facial nerve, Nerve conduction study, Electrodiagnosis, Active electrode sites