Nine patients, 3 men and 6 women, ages 39 to 61, were operated on between May 1978 and August 1978 for classical hemifacial spasm. The operation consisted of a small retromastoid craniectomy performed through a short vertical incision with microsurgical exploration of the cerebello pontine angle and vascular decompression of the facial nerve root exit zone. Decompression was maintained by interposing a small piece of muscle between the artery and the brain stem. Five patient have had complete relief of the hemifacial spasm. Three patients have had partial relief of the hemifacial spasm. One patient have had no relief of the hemifacial spasm.