Objective: To study the relationship between the facial nerve root and its surrounding vessels. Material and Methods: Forty-nine facial nerve roots and surrounding vessels were dissected and observed under an operating microscope. Results: The facial nerve root and its surrounding vessels were compressed in 24.5% (12/49) of cases; there was contact between them in 14.3% (7/49) of cases. The main vessels compressed by or in contact with the facial nerve root were the anterioinferior cerebellar artery (AICA, 68.4%), the posterioinferior cerebellar artery (PICA, 4.1%), the malformed vertebral artery (4.1%) and the anterioinferior cerebellar vein. Conclusion: The compression of the facial nerve root by surrounding vessels may be the main cause of hemifacial spasms.