The in vivo effect of topical clobetasol-17-propionate (CP) on the leukotriene B4- and trauma-induced intra-epidermal accumulation of polymorphonuclear leukocytes (PMN) was investigated in normal volunteers. PMN accumulation was assessed using elastase, a specific and sensitive marker for these cells. A profound inhibition of PMN accumulation was shown in the first 2 days of treatment with CP, an effect that faded away after a treatment of 2 weeks.