This is the first reported case of a major overdose of Lioresal (baclofen or CIBA BA-346467). A 29-year-old woman with known Huntington's disease took from 900 to 970 mg of Lioresal, a cogener of gamma amino butyric acid (GABA) used experimentally to treat muscle spasm. She was admitted in deep coma with absent brain stem reflexes and without spontaneous respiration, and she required cardiovascular support. Her pupils were fixed at 3 mm and unreactive for 48 hours. She continued to require intensive support for a total of 72 hours and had one seizure during the recovery phase. Her eventual recovery was complete. No specific antidotes are currently available for overdose of Lioresal and supportive care is the only method of treatment for overdose.