Roseola infantum, also known as exanthem subitum or sixth disease, is a generally benign febrile exanthem of infancy. It has a characteristic clinical course of high fever followed by the appearance of an exanthem upon defervescence. Febrile seizures are a frequent complication. Roseola is caused by infection with human herpesviruses 6 or 7 (HHV-6/7), which are acquired at a young age. Diagnosis is made by serology or by virus detection in body fluids and tissues. Treatment of roseola is supportive; recovery is usually complete with no significant sequelae. However, HHV-6/7 can reactivate in immunocompetent as well as immunocompromised individuals with severe systemic consequence.