Objective: The 5-lipoxygenase products, especially sulfidopeptide leukotrienes take an important role in the pathogenesis of asthma. The effects of two selective 5-lipoxygenase inhibitors, acetohydroxamic acid derivative BWA 4C and a naphtokinon derivative CGS 8515, were investigated for their effect on antigen-induced contraction in ovalbumin sensitized guinea-pig isolated tracheal tissues. Material and Methods: The study included 15 male guinea pigs. They were actively sensitized by the Modified Andersson Method, including two standard 0.5 mL injections of a solution containing 20 mu g ovalbumin and 50 mg aluminium hydroxide in saline on day 0 and day 14. Twenty-one to 27 days after the injection of ovalbumin, the tracheal rings from sensitized guinea pigs were exposed to antigen, and the possible inhibitor effects of 5-lipoxygenase inhibitors on the antigen-induced contraction were examined in water-jacketed tissue baths containing Krebs buffer. Results: Both BWA 4C and CGS 8515 significantly reduced antigen-induced tracheal contraction compared to control groups. Conclusion: As both CGS 8515 and BWA 4C inhibit antigen induced tracheal smooth muscle contractions, they may take an important role in the treatment of asthma and related inflammatory events.