Immune response to ultraviolet radiation-modified skin antigens has been suggested as a pathomechanism of skin lesions in discoid lupus erythematosus and polymorphous light eruption. In order to elucidate the role of T-lymphocyte subsets in this response, we studied the distribution of CD45RO+, CD45RA+ and CD31+ cells and the endothelial expression of adhesion molecules E-selectin/P-selectin, intercellular adhesion molecule-1 and CD31 antigen in photoprovoked and spontaneous skin lesions. Typically, CD45RA+ cells were the prevailing inflammatory cell population of discoid lupus erythematosus, whereas CD45RO+ cells prevailed in both diseases and in healthy controls. Epidermotrophism of any T-cell subsets was more typical of discoid lupus erythematosus, whereas no major differences in endothelial adhesion molecule expression was found between the 2 diseases. Strong keratinocyte ICAM-1 expression was associated with adjacent CD45RO+ cell infiltrates, not with CD45RA+ or CD31+ cell infiltrates. We conclude that the cellular immune response to UV radiation is dissimilar in discoid lupus erythematosus and polymorphous light eruption.