Aspirin intolerance is characterized by polypous rhinosinusitis, bronchial asthma and adverse reactions to aspirin. The common intolerance to all cyclo-oxygenase inhibitors allows us to focus study of the pathogenesis of AI on the metabolism of arachidonic acid. Nasal polyposis is a chronic inflammatory condition that is mostly characterized by an infiltration of eosinophils. How this eosinophilic inflammation leads to polyp formation remains largely unclear. Eosinophils are the major source of cysteinyl leukotrienes--potent pro-inflammatory mediators they can by responsible for nasal blockade, rhinorrhoea and hyperresponsiveness. A role of prostaglandins (PGs) and leukotrienes (LTs) in the pathogenesis of nasal polyps has been recently suggested and leukotriene levels have been shown to be elevated in patients with asthma as well as in those with sinonasal polyposis and sinusitis. Because leukotriene receptor antagonists inhibit activity of endogenous leukotrienes and decrease tissue eosinophilia it is speculated that these drugs may be useful also in the management of nasal polyps. Our study was designed to determine the efficacy of zafirlukast, a cysteinyl leukotriene receptor antagonist, in nasal polyposis. We conclude that antileukotrienes might play a role in controlling polyposis and their symptoms, and they might be a alternative to long-term steroid therapy and repeated surgical therapy.