Wernicke's encephalopathy may be fatal if untreated. Because Wernicke's encephalopathy is suspected to be underdiagnosed in children, the authors wished to assess the frequency of overlooked diagnosis and to establish pertinent findings that could lead to early identification of pediatric Wernicke's encephalopathy. The authors performed multiple literature searches seeking pediatric patients with Wernicke's encephalopathy (age = 20 years or younger). A total of 30 patients was found, and the authors added a new patient. Each case report had its clinical, radiologic, and laboratory data, diagnostic method, and outcome analyzed. Of 31 patients, 16 were female and 15 male; the median age +/- S.D. was 11 +/- 6.5 years. The most frequent underlying disorder was malignancy in 11. Thirteen patients died undiagnosed, 16 recovered with thiamine therapy (eight with sequelae), and two died of infection soon after thiamine replacement was initiated. Only six presented with the Wernicke's encephalopathy clinical triad (mental status changes, ocular signs, and ataxia) at neurologic onset; nine eventually demonstrated this triad. The high rate of patients diagnosed only at postmortem examination (41.9%) confirms that Wernicke's encephalopathy is underdiagnosed in children. Thiamine therapy is warranted if any component of the Wernicke's encephalopathy triad is present in an appropriate clinical setting.