This is areport of a 10-year-old female neutered Doberman Pinscher with a clinical diagnosis of myelopathy. The dog was anesthetized using oxymorphone, thiopental, and halothane in oxygen for a cerebrospinal tap and a myelogram. Iohexsal injection into the subarachnoid space by lumbar puncture was uneventful. Additional iohexal was given into the cerebellomjedullary cistern. Immediately following iohexal administration into the cerebellomedullary cistern, several electrocardiographic changes occurred. Two extended periods of asystole responded to intravenous glycopyrrolate administration. A slow multiform ventricular escape rhythm was established after the second dose of glycopyrrolate. Ultimately, atrial activity with apparent A V dissociation resumed, atrial fibrillation developed, and the rhythm converted to normal sinus rhythm. The dog had a normal cardiac examination the following day. Two days later, the dog was anesthetized using a similar anesthetic regimen with maintance on isoflurane in oxygen for a hemilaminectomy. The dog recovered uneventfully from surgery and was discharged 2 days later.