The various clinical features of adult T-cell leukemia/lymphoma (ATL) are frequently accompanied by skin eruptions. Recently, a cutaneous type of ATL has been proposed by clinical studies. We analyzed the viral integration of human T-cell leukemia virus-I (HTLV-I) and monoclonal rearrangement of T-cell receptor (TCR) gene in blood lymphocytes and the cutaneous infiltrated cells of nine ATL patients with various clinical features and skin eruptions. We classified them by the results of Southern blot analysis and propose a cutaneous-type ATL accordingly. In two of them, we could detect the monoclonal integration of HTLV-I and T-cell monoclonality only in the skin but not in the peripheral lymphocytes. We also demonstrated the time course study in one patient. Clinicians should be aware of the HTLV-I positive cutaneous T cell lymphoma that can be named cutaneous-type ATL. Examination of viral integration and T-cell monoclonality in skin lesions is required to make an exact diagnosis of cutaneous ATL.