A case of Bowen's disease (BD) that appeared in the perianal region of a 65-year-old Japanese woman coexistent with chronic adult T cell leukemia (ATL) is described. Histopathological findings revealed that irregularly arranged tumor cells with atypical nuclei throughout the epidermis, which itself disclosed hyperkeratosis, dyskeratotic cells, and clumping cells. Positive staining for HPV antigens was immunohistochemically seen in several nuclei of the tumor cells. Electron microscopic study of the tumor tissue disclosed virus particles of about 50 nm in diameter form the squamous cells. A positive band at 256 bp was obtained by PCR using HPV-L1 primer. The amplified DNA by L1 primer completely corresponded to that of HPV-58.