Objective: To study the relationship between the trigeminal nerve root and its surrounding vessel. Materials and Methods: Sixteen head specimens infused with red gelatin into an artery were dissected and observed under an operating microscope. Results: The trigeminal nerve root and its surrounding vessel (superior cerebellar artery and anterior inferior cerebellar artery) creating contact was found to be 50.0% (16/32); forming compression was found to be 12.5% (4/32). Conclusions: Vascular compression may be the predominant cause of trigeminal neuralgia.