Various cytokines have in the past been detected in human skin. Among these, the neutrophil-activating peptide NAP-1/IL-8 is a potent 8-kD proinflammatory peptide that has been purified from psoriatic scales. Its chemotactic activity on human neutrophils, as well as its presence in psoriatic scales, may relate to a role in this disease. In the present study, the tissue distribution of the peptide was examined immunohistochemically using two monoclonal antibodies (52E8, 46E5) recently produced and characterized in our laboratory. Immunoreactivity was detected in both normal and psoriatic skin, resulting in uniform suprabasal keratinocyte staining in normal skin with 52E8 and of all keratinocytes with 46E5. Immunoreactivity in psoriasis correlated to the inflammatory tissue reaction, varying from uniform absence in highly active psoriasis to focally weak staining in plaque type psoriasis. Cells of the acrosyringium and hair follicles were always positive and were unaffected by the inflammatory activity. Epidermal immunoreactivity detected in this study may be associated with closely related peptides of the IL8 family or with truncated or extended forms of NAP-1/IL-8.