The transepidermal migration of polymorphonuclear leukocytes is a well established target for antipsoriatic therapies. Tetracycline, although inhibiting the movement of PMN, is not an effective treatment for psoriasis. In contrast to the inhibition of PMN chemotactic response to serum and bacterial products, the leukotriene B4-induced and trauma-induced intraepidermal accumulation of PMN was unaffected by tetracycline.