Systemic retinoids are effective in a variety of inflammatory dermatoses. Disorders in which polymorphonuclear leukocytes (PMN) are involved, such as psoriasis and acne, respond particularly well to various retinoids. However, side-effects restrict the use of systemic retinoids to severe manifestations. Topical application might provide the possibility of avoiding the systemic sideeffects of these compounds. In this communication we report on the modulation of transepidermal migration of PMN by topical application of all-trans-retinoic acid, 13cis-retinoic acid, arotinoid methyl sulphone and arotinoid ethyl sulphone. Test areas of healthy volunteers were pretreated with these retinoids in a cream base and with corresponding placebo creams, and intraepidermal accumulation of PMN was quantified 24 h after epicutaneous challenge with leukotriene B 4 (LTB4), using elastase as a marker enzyme. Topical treatment with 13-cis-retinoic acid resuited in a marked and statistically significant inhibition of the LTB4-induced migration of PMN. All-trans-retinoic acid, arotinoid methyl sulphone and arotinoid ethyl sulphone reduced the accumulation of PMN slightly, but not statistically significantly. Topical treatment with arotinoid methyl sulphone had no effect.