Surgical treatment of hemifacial spasm associated with tortuous vertebrobasilar system was reported. A patient was 63-year-old female, who first experienced mild and intermittent muscle twitching around her left eye twenty years prior to admission. Five years later, the twitching extended to all the facial muscles on the left side. She was treated with facial nerve block, which resulted in facial palsy for about one year. Because of recurrence of the hemifacial spasm, she was admitted to the Neurosurgical Department of Bokuto Municipal Hospital on October 12, 1977. Neurological examination revealed no abnormalities except for left hemifacial spasm with slight muscular weakness. Electromyogram showed severe twitching and synkinesis of all the muscles of facial expression. Vertebral angiogram on the left side disclosed pronounced elongation of the vertebral and basilar arteries, which extended into the left cerebellopontine angle. Compression of the facial nerve root exit zone at the brainstem by the vertebral artery was considered to be the cause of the hemifacial spasm. Suboccipital craniectomy was carried out on November 29, 1977. The vertebral artery extended into the cerebellopontine angle, and adhered to the facial nerve. After mobilization of the vertebral artery from the facial nerve, a small prosthesis of non-absorbable spongy material (Teflon felt) was interposed between the vertebral artery and brainstem. Postoperatively, the hemifacial spasm disappeared, but the facial palsy, which had been observed preoperatively probably due to previous facial nerve block and long-standing hemifacial spasm, remained. The function of the acoustic nerve was preserved. Recently vascular compression of the facial nerve root exit zone has been reported as a major cause of hemifacial spasm, but such abnormal vessels are rarely demonstrated angiographically.