Nonallergic rhinitis is a complex of syndromes that are united by the absence of atopic, T(H)2 lymphocyte, immunoglobulin E (IgE)-mediated mechanisms. We propose a classification system based on the presence or absence of inflammatory granulocytes. Eosinophilic nonallergic rhinosinusitis may also be called chronic eosinophilic sinusitis syndromes (CESS) to help classify these disorders in which diverse mechanisms of eosinophil chemoattraction and survival predominate. Allergic fungal sinusitis, eosinophilic nasal polyps, aspirin sensitivity, and related disorders would fit in this category. Accumulation of neutrophils occurs in chronic infectious rhinosinusitis, foreign body reactions, and immunodeficiencies. More complex and variable combinations of leukocytes are found in Wegner's granulomatosis and related syndromes, and during the evolution of viral infections. The noninflammatory disorders can be divided by mechanism into hormonal; sympathetic dysfunction (including antihypertensive adrenergic drug therapy); cholinergic rhinitis; and nociceptive syndromes with hyperalgesia and other features (eg, the nonallergic rhinitis of chronic fatigue syndrome). Therapy based on the most likely pathophysiologic mechanism is anticipated to have the most success, but requires acceptance of the wide differential diagnosis of nonallergic rhinitis and rejection of the obsolete term of "vasomotor rhinitis."