Reported is a case of Brown-Sequard syndrome following attempted heroin injection into the right external jugular vein. A right-sided hemiparalysis with a contralateral sensory loss of touch, pain, proprioception, and temperature developed over several hours to the C3 dermatome level. A myelogram showed a vasculitis pattern in the lower cervical region. Treatment was with high-dose dexamethasone for ten days. After six weeks of inpatient physical therapy, only minimal motor and sensory return was seen. Although this syndrome is usually due to lateral hemisection of the spinal cord by a stab wound or a gunshot wound, in this case we believe it resulted from chemical transection due to the heroin or quinine diluent or both.