Wernicke encephalopathy is a disorder caused by a deficiency of thiamine which is a cofactor of several metabolic enzymes. The symptoms include mental confusion, ataxia, and ocular signs in adults, infants, and children. Patients often have somnolence and weakness combined with ophthalmoplegia. Alcoholics are the best known risk group; however, Wernicke encephalopathy occurs in poorly nourished patients of all ages. We present 2 children with malignant disease in whom Wernicke encephalopathy--an underdiagnosed and potentially fatal, but preventable and treatable disease--was diagnosed postmortem.