We report on two Japanese siblings (one female and one male) with PEHO syndrome (progressive encephalopathy with edema, hypsarrhythmia, and optic atrophy). They showed profound generalized hypotonia early in infancy and developed infantile spasms with hypsarrhythmia within the first year of life. Abnormal eye movement and visual failure with optic atrophy were also observed early in infancy. Psychomotor development was arrested and serial neuroradiological studies showed slight progressive brain atrophy, dominantly of the brainstem. This is the first case report of PEHO syndrome, other than those dealing with the Finnish population.