Over the last several years, important research has demonstrated the link between the upper airways disease, rhinitis, and lower airways disease, asthma. In fact, it appears that asthma and rhinitis represent components of a single inflammatory airways disease. With the use of epidemiologic data and pathophysiologic studies, the connection between these inflammatory conditions becomes clear. Numerous population studies show the high rate of asthma in patients with allergic rhinitis compared to the general population. Several surveys suggest the rate of rhinitis in asthma patients to be as high as 100%. Recent studies in humans demonstrate that local allergen exposure in the nose of patients with allergic rhinitis can quickly lead to significant allergic inflammation in the lungs, even without a previous history of asthma or airways bronchial hyperreactivity. It is important for the clinician to understand the connection between these disorders so that all patients with rhinitis are evaluated for lower airways disease, and all patients with asthma be screened for upper airways conditions.