A 24-year-old pregnant woman started to have severe hyperemesis gravidarum at 6 weeks' gestation. Six weeks later, dizziness, ataxia, visual disturbance, diplopia and confusion were developed. On admission, she presented ophthalmoplegia, nystagmus, deaeased tendon reflex, intention tremor, ataxia, confusion and memory disturbance. She was diagnosed to Wernicke-Korsakoff syndrome and 100mg of thiamine was administered intravenously daily till 28 weeks gestation and then intramuscularly. Her ocular symptns, together with neurological signs, were gradually improved. Memory disturbance slightly improved but remained at the time of delivery. The case will be presented in more details with a brief revie of literatures.