Vitiligo is an acquired, progressive depigmenting disorder of unknown etiology. In this study, to clarify pathogenesis of vitiligo, the marginal skin of actively spreading and stable vitiligo was examined using ICAM-1, HLA-DR, CD4 and CD8 monoclonal antibodies. In immunohistochemical study, ICAM-1 was expressed in four of five epidermis in active lesions, but not in stable lesion. Dermal ICAM-1 was also expressed in all active and stable lesions. HLA-DR was also expressed in all active epidermis in active lesions, but two of five epidermis in stable lesion. Dermal HLA-DR was also expressed in all active and stable lesion. CD4 lymphocytes were expressed more strongly in active lesion, but CD8 lymphocytes were not different in both lesions. There was no significant difference of degree of positivity with CD4 and CD8 in normal control specimens. In conclusion, we think that ICAM-1 and HLA-DR expression, cytokines released from keratinocytes, melanocytes or lymphocytes and infiltration of activated T-lymphocytes play an important role in disease activity.