The features of a characteristic type of encephalopathy caused by human herpesvirus-6 are presented. All patients have clusters of brief convulsions during the stage of skin eruptions. Sometimes the encephalopathy resulted in hemiplegia or mental retardation. Because the clinical course is similar, we propose a subtype of encephalopathy "human herpesvirus-6 encephalopathy with cluster of convulsions in eruptive stage" for further studies of pathophysiology and treatment.