A 23-year-old man, involved in a motor-vehicle accident, became quadraparetic due to cervical spinal cord injury at the C-4 to C-6 level. Five months later he was noted to have bilateral, asymmetric pupillary mydriasis precipitated by elevation and stretch of an arm or leg. Pharmacologic pupillary testing and ciliospinal reflex responses suggested that the oculosympathetic pathways were intact. Computed tomographic myelography using metrizamide disclosed a posttraumatic syringomyelic cyst at C-4. This pupillary phenomenon has been termed oculosympathetic spasm, and we reviewed four previous reports. While the cause of oculosympathetic spasm remains speculative, it may represent a localized form of autonomic hyperreflexia. © 1984, American Medical Association. All rights reserved.