The effect of a thromboxane A2 synthetase inhibitor (OKY-046, 400 mg po/day) on mucociliary transport was investigated in 19 asthmatic patients. The nasal clearance time, as measured by the saccharin test, was prolonged in asthmatics (60.2 +/- 8.4 SE min) compared with normal controls (15.1 +/- 3.4 SE min). Within 4 weeks after OKY-046 administration, the nasal clearance time had improved (27.4 +/- 4.4 SE min, P less than .01) and the amount of sputum had decreased 30% (P less than .01). These results indicate that thromboxane A2 plays an important role in mucociliary transport in patients with asthma.