Abstract. Nonallergic rhinitis with eosinophilia syndrome (NARES) is a clinical syndrome comprising symptoms consistent with allergic rhinitis in which an absence of atopy has been demonstrated by allergen skin testing, and nasal cytology analysis demonstrates more than 20% eosinophils. Anosmia is a prominent feature not shared with allergic rhinitis. The pathophysiology of NARES is poorly understood, but a key component involves a self-perpetuating, chronic eosinophilic nasal inflammation with development of nasal micropolyposis and polyposis. Mast cells likely play an important role as well. NARES is a risk factor for the development of nasal polyposis and aspirin sensitivity, as well as obstructive sleep apnea. Treatment consists mainly of intranasal corticosteroids with or without the addition of second-generation antihistamines and/or leukotriene-receptor antagonists.