Proteus syndrome is a rare hamartomatous syndrome with a variety of abnormalities. A 6-year-old Japanese boy without apparent abnormalities at birth developed by 1 year of age cerebriform skin tumors on the right sole, soft masses on the left sole, palms and fingers, brownish verrucous lesions and whorled brownish patches on the right side of the neck, chest, external genitals and extremities, hemihypertrophy of the right lower extremity, lordoscoliosis, protuberance of the skull, epileptic seizures, hydrocephalus and mental retardation. This patient appears to be the second Japanese case of Proteus syndrome.