Erythromycin inhibits mucus glycoconjugate secretion from airway cells in vitro and may increase mucus clearance in patients with asthma or diffuse panbronchiolitis. Because mucus hypersecretion is common in purulent rhinitis, we questioned whether clarithromycin would change the properties of nasal mucus from subjects without sinus disease and from patients with acute purulent rhinitis. Nasal secretions were collected before and after nasal methacholine challenge from 10 adults without nasal symptoms and without methacholine from 10 patients with purulent rhinitis. After 2 wk of oral clarithromycin (500 mg twice daily), secretions were again collected from both groups. Secretions were analyzed for viscoelasticity, cohesion, hydration, and ciliary and airflow (sneeze) transportability. Compared with secretions from healthy subjects, rhinitis secretions had decreased wettability (contact angle on Teflon 100 degrees versus 84.67 degrees; p = 0.001), increased cohesion (36.8 versus 24.3 mm; p = 0.003), decreased sneeze clearability (20.6 versus 32 mm; p = 0.04), and increased percent solids (4.61 versus 2.82%; p = 0.04). After clarithromycin, the rheology, hydration, cohesion, and transportability of the rhinitis secretions were similar to those of the postclarithromycin secretions from the healthy subjects. Secretion volume also decreased (500.1 versus 28.3 mg; p = 0.01), and mucociliary transportability increased by 30% (0.76 versus 0.99; p = 0.005). Although clarithromycin reduced mucus secretion in both rhinitis patients and normal subjects, it did not alter the secretory response to methacholine.