An 18-month-old boy was admitted in April, 1988 because of a penile mass which had been first noted at the age of one month. From nine months after birth, transient bleeding from the mass accompanied by pain had been occasionally noted. At the age of 14 months, the mass seemed to grow markedly. On physical examination, there was an irregularly shaped mass on the right side of the prepuce. It was palpated subcutaneously, soft in consistency and was 10 mm in diameter. It had a light-purple color. Upon surgery, the mass was found not to have originated from the cavernous body of the penis, so that it could be excised without difficulty. Histopathological diagnosis was cavernous hemangioma. Electron microscopic examination revealed findings suggestive of newly formed blood vessels such as abnormal cuboidal shape of endothelial cells and a high nucleocytoplasmic ratio. Immunohistochemical examination of factor VIII-related antigen was in homogeneously positive in vascular endothelial cells. To our knowledge, this is the twenty-eighth case reported in Japan.