Allergic rhinitis and asthma are linked by epidemiologic, histologic, physiologic, and immunopathologic characteristics and by a common therapeutic approach. Epidemiologically, the disorders often coexist. Histologically, the upper and lower airways are lined, and linked, by the respiratory epithelium. Physiologically, they may be linked by the nasobronchial reflex. Pathologically, they are linked by similar early- and late-phase allergic responses throughout the airways and by the systemic immunologic response to airborne allergens. Uncontrolled allergic rhinitis may be associated with worsening of coexisting asthma, and optimal treatment of allergic rhinitis may improve coexisting asthma. The key to managing both disorders is prevention and relief of chronic allergic inflammation in both the upper and lower airways. The similarities between allergic rhinitis and asthma outweigh the differences. To facilitate appropriate recognition and treatment of the common inflammatory process throughout the airways, consideration should be given to introducing the new term "allergic rhinobronchitis."