OBJECTIVE: To investigate the difference in mucociliary clearance and surface mucosal structure of the nasal septum and lateral nasal wall in patients with and without septal deviation. METHOD: The saccharine-dye test was used to measure the mucociliary clearance time in both nasal cavities of 20 patients with nasal septal deviation (study group) and was compared with that of 30 patients without septal deviation (control group). Bilateral septal and lateral nasal wall mucosal biopsies were taken from the study group during septoplasty, and unilateral biopsies were taken from 10 of the control group. These biopsies were studied under the scanning electron microscope. RESULTS: In the study group, mucociliary clearance on the side opposite the septal deviation was significantly slower than on the other side. Mucociliary clearance on both sides of the deviated septum of the study group was significantly slower than clearance in the control group. There was no statistically significant difference in the distribution of mucosal cilia of the cavities on either side of the deviated septum in the study group, nor between the distribution in the study group and controls. CONCLUSION: Patients with septal deviation display no change in mucosal surface anatomy but have decreased mucociliary activity on both sides of the deviation, the least activity being on the side opposite the deviation. © 2006 The American Laryngological, Rhinological and Otological Society, Inc.