Although mucociliary clearance has been shown to be impaired in patients with allergic rhinitis and chronic rhinosinusitis, its exact role in relation to a predisposition to rhinosinusitis is unknown. To investigate this possible association, we conducted a prospective study of 125 patients with allergic rhinitis. Of this group, 23 patients were classified as being sinusitis-prone based on their history of antibiotic consumption for the treatment of rhinosinusitis; the remaining 102 patients were deemed to be not sinusitis-prone. The saccharine test was used to evaluate mucociliary clearance in all patients. Several variables-age, sex, smoking habits, rhinitis severity, and medication history-were examined. We found that the sinusitis-prone patients had a significantly greater mucociliary clearance time than did those who were not prone (median: 15 and 12 min, respectively; p = 0.02). No other statistically significant differences were seen between the 2 groups with respect to any other variables that might have affected mucociliary clearance. We conclude that impaired mucociliary clearance in allergic rhinitis patients is associated with a predisposition to rhinosinusitis.