Subacute sclerosing panencephalitis (SSPE) usually begins insidiously and follows a subacute course with relentless but slow progression to death. In recent years, however, patients with acute or fulminant course were reported. In this article, we report on three patients (2 girls, 1 boy) with SSPE who developed an acute and fulminant course. Subacute sclerosing panencephalitis may be seen with more atypical symptoms and more acute and fulminant courses due to various undetermined reasons. Early diagnosis is very important for the effectiveness of treatment. Children presenting with acute or subacute neurologic symptoms should be examined for SSPE, especially if they have no risk factors for hereditary neurodegenerative/ neurometabolic diseases, and it is more important if those children were not vaccinated or were infected with measles.