Acute necrotizing encephalopathy is a fulminant neurologic disease seen predominantly in Japan and Taiwan. We present two cases diagnosed at a Canadian center within the same year in Caucasian children. Both were previously well, developed an acute viral illness with fever and vomiting, and progressed to brain death within 2 to 4 days. Neuroimaging and postmortem examination demonstrated the unique features of bilateral and severe necrosis of deep gray-and subcortical white-matter structures. The first case was associated with extensive, but transient, hepatic involvement, recent varicella and rotavirus infections, and detailed metabolic studies, including mitochondrial functional analysis, were normal. The second case tested positive for influenza A infection, whereas evidence of liver damage was lacking. Both children demonstrated early lymphopenia and myocardial necrosis, two features not previously associated with acute necrotizing encephalopathy. These cases are unique in their occurrence in non-Japanese children and are among the first published reports in Canada. ( J Child Neurol 2005;20:527-532).