The vast majority of patients with asthma have rhinitis, and rhinitis is a major independent risk factor for asthma in cross-sectional and longitudinal studies. The relationships between rhinitis and asthma can be viewed under the concept that the 2 conditions are manifestations of one syndrome, the chronic allergic respiratory syndrome, in 2 parts of the respiratory tract. At the low end of the syndrome's severity spectrum, rhinitis appears to be the sole manifestation, although pathologic abnormalities in the lower airways are already present. At the higher end, rhinitis is worse, and the lower airways disease becomes clinically evident. Once manifested, the 2 conditions track in parallel in terms of severity. This parallel relationship is influenced by many interactions between the nasal and the lower airways: some interactions stem from the fact that the nasal passages play a major homeostatic role by conditioning inhaled air, but perhaps even more important is the bidirectional interaction that results from the systemic inflammation that is produced after local allergic reactions. Successful management of the chronic allergic respiratory syndrome requires an integrated view of the airways and an understanding of their interactions.