The topical corticosteroids are widely used in the treatment of moderate psoriasis, because of their usefulness for reducing inflammation and controlling itching. The therapeutic effect of corticosteroids in different cutaneous inflammatory diseases may be partially explained by their varying ability to block in vitro the synthesis of different cytokines, which play a pivotal role in epidermal hyperproliferation and leukocyte recruitment into the skin. The purpose of the present investigation was to further elucidate the mode of action of mometasone furoate, a medium-high potency, topical corticosteroid, on adhesion molecules, cytokines and cytokine receptor expression in psoriatic skin. Using an immunohistochemical assessment, we examined lesional skin biopsies from ten psoriatic patients before treatment and after 1 and 3 weeks of therapy. The overexpression of alpha 2, alpha 3, alpha 6, and beta 1 integrins detected in the spinous layer of untreated psoriatic skin was significantly decreased after therapy in 8 out of 10 cases, characterized by only partial clinical remission. In the remaining patients, a disappearance of the above integrin reactivity paralleling the disappearance of psoriatic lesions was induced by the treatment. With the exception of GM-CSF, no or only marginal effects of mometasone furoate on the cytokine and cytokine receptor system were observed. A significant reduction of the positive immunostaining with anti-ICAM-1 and ICAM-2 monoclonal antibodies on dermal vascular endothelial cells was also seen. Thus, our findings indicate that the therapeutic effects of mometasone furoate in psoriasis are mediated principally by decreasing adhesion molecule expression and to a lesser degree by inhibiting cytokine synthesis.