The possible utility of DuP 654, a potent 5-lipoxygenase inhibitor, for treating human inflammatory skin disease was investigated in murine skin treated with 1.0 mg arachidonic acid (AA). When DuP 654 was applied to murine skin treated with AA, it inhibited the resulting inflammation and influx of cells. High performance liquid chromatography and radioimmunoassay analysis of lipid extracts from AA-treated ears indicated that the influx of polymorphonuclear leukocytes (PMN) was temporally preceded by an appearance of significant amounts of 5-HETE (6.7 ± 1.4 ng/ear) and Leukotriene B4 LTB4 0.92 ± 0.2 ng/ear) when compared with extracts of untreated ears (5-HETE, 02 ± 0.3 ng/ear; LTB4, < 0.1 ng/ear). The levels of the 5-lipoxygenase products were reduced by treatment with 10 µg/ear DuP 654. Lipid extracts from AA-treated ears contain chemotactic activity for human PMN and this chemotactic activity in the AA-treated ears could be reduced but not eliminated by immunosorption with anti-LTB4 antibodies coupled to protein A-agarose. The appearance of the chemotactic activity was inhibited by DuP 654. Taken together, these data suggest that DuP 654 may have utility in human inflammatory skin dise