Background: Nitric oxide (NO) plays an important role as an inflammatory mediator in the airways. Inducible NO synthase in the nasal mucosa is upregulated in perennial allergic rhinitis, and nasal NO is reduced after treatment with topical corticosteroids. A previous study has suggested that there is a significant correlation between exhaled NO and sputum eosinophils in patients with asthma. Objective: We investigated the ability of intranasal administration of eotaxin, a potent chemoattractant for eosinophils, to induce eosinophil accumulation and the relationship between eosinophil recruitment in the nasal mucosa and nasal NO production in patients with allergic rhinitis. Methods: Nine patients with allergic rhinitis were studied. Eotaxin or diluent was delivered intranasally in patients by using a metered spray pump. Nasal NO, symptom scores, and the influx of inflammatory cells in nasal lavage fluid were assessed before and after the challenge. Immunoreactivity for inducible NO synthase and nitrotyrosine was evaluated in nasal lavage cells. Results: Eotaxin induced a significant influx of eosinophils (P < .05) with mild symptoms of rhinitis. There was neither significant migration of lymphocytes, basophils, and macrophages into nasal lavage fluid nor a shedding of nasal epithelial cells after eotaxin challenge. Nasal NO was increased significantly (P < .05) 8 hours after eotaxin challenge compared with diluent challenge. Nitrotyrosine immunoreactivity was moderately elevated in nasal epithelial cells after the challenge. Conclusion: We have shown that eotaxin causes chemotaxis of eosinophils with a clinically symptomatic inflammatory response in the nasal mucosa and that eosinophil recruitment accompanies an increase in nasal NO, contributing to oxidative stress. (J Allergy Clin Immunol 2000;105:58-64.)