Forty patients were studied to investigate the effect of nasotracheal intubation on nasal mucociliary clearance measured with the radiopaque disc method under standard conditions. Postoperative mucociliary slowing on the intubated side was observed in 65% of patients. Difficult or prolonged intubation increased the incidence of mucociliary stasis. Age, sex, smoking history, tube size and the use of lubricants had no effect. Postoperative slowing of the clearance rate was most probably the result of mechanical trauma to the superficial epithelial layers, and recovery of function was reasonably rapid with conservative management.