A report is presented on a patient with Wernicke's encephalopathy secondary to hyperemesis gravidarum. The 25-year-old female presented 11 weeks into pregnancy with prolonged vomiting. Neurological examination 8 weeks later demonstrated obtunded sensations, nystagmus and ataxia of gait. MR imaging revealed bilateral lesions in the mediodorsal nuclei of thalami, in the hypothalamus and in the periaqueductal gray matter (1). The neurological signs and the MRI findings pointed to a diagnosis of Wernicke's encephalopathy. The patient was treated with intramuscular vitamin B1 followed by oral thiamine until the end of pregnancy. The subsequent course of the pregnancy was uncomplicated, and resulted in the delivery of a healthy 2970 g male infant. A review of the literature published during the last 30 years revealed an additional 20 cases of Wernicke's encephalopathy induced by hyperemesis gravidarum. Only half of these pregnancies resulted in the birth of a normal infant.