A case report is presented on a patient with Wernicke's encephalopathy secondary to hyperemesis gravidarum. The 30-year-old woman was admitted with a severe dehydrated state, ataxia, dizziness at 17 weeks. Neurologic examination demonstrated nystagmus, gait ataxia, paresthesia. The MR imaging revealed the high signal intensity in both hypothalamus, thalamus, midbrain. The neulolgic signs and MRI findings pointed to diagnosis of Wernicke's encephalopathy. The patient was complicated with hyperthyroidism. The patient was treated with parenteral thiamine and prophylthyiouracil. The pregnancy was terminated by spontaneous abortion at gestationl 18 weeks. A review of the literature published during the last 30 years revealed an additional 25 cases.