summaryA specific peptidoleukotriene receptor antagonist, Ro 23‐3544, was tested for its efficacy in modulating DNFB‐induced allergic and croton oil‐induced irritant contact dermatitis in mouse ears. Treatment shortly after elicitation of the dermatitis, and for up to 5 days thereafter, was moderately effective in suppressing DNFB‐induced ear swelling in a dose‐dependent fashion. Daily pre‐treatment of the ears for 1 week caused a more marked reduction of DNFB‐induced ear swelling during the first 48 h after elicitation. No reduction, but rather an increase in ear swelling was observed with croton oil‐induced dermatitis. These results indicate that peptidoleukotrienes play a role in the early stages of elicitation of murine allergic, but not irritant contact dermatitis and that a specific receptor antagonist can only partially reverse the effect of peptidoleukotrienes once the dermatitis