A patient with chronic actinic dermatitis showed a leukocytosis with peripheral atypical lymphocytes. Histology of cutaneous eruptions disclosed a dense infiltrate of lymphocytes mixed with large hyperchromatic cells in the dermis and Pautrier-like microabscesses in the epidermis. However, clonal rearrangements of the T-cell receptors were not detected. On the other hand, monoclonal integration of human T-cell lymphotrophic virus type I provirus was found in the peripheral lymphocytes. In the present case, pseudolymphomatous changes occurred in association with adult T-cell leukemia. Southern blot analyses were useful for the correct diagnosis.