The effects of aerosolized distilled water and isosmolal dextrose in the isolated larynx on laryngeal muscle activity were studied in eight anesthetized dogs. Water aerosol was associated with an increase in peak posterior cricoarytenoid activity but no change in thyroarytenoid activity. Saline or isosmolal dextrose aerosols did not have any effect on the activity of either muscle. The reflex increase in posterior cricoarytenoid activity due to laryngeal negative pressure was enhanced when the negative pressure challenge was repeated following distilled water aerosol. The results suggest that alteration in laryngeal surface liquid composition modifies the response of pressure-responsive laryngeal receptors and, thereby, the reflex activation of airway patency maintaining muscles.