Results of intracordal Teflon injection for symptoms of unilateral vocal cord paralysis have been excellent. There seems to be no significant long-term foreign body reaction or limitation to maximum airflows. However, acute inflammatory reactions and airflow obstruction have been reported. The objective of the present study was to evaluate the frequency, extent, and duration of airway obstruction following Teflon injection. Forced inspiratory and expiratory airflows were measured in seven consecutive patients before, 24 hours, and 10 days after Teflon injection. Significant variable upper airway obstruction, as demonstrated by an increase in the ratio of forced expiratory airflows at 50% Vital Capacity to the forced inspiratory airflows at the same lung volume (VE50/VI50), was found in each subject. At 24 hours after the injection this ratio increased from a baseline of .098 +/- 0.50 (mean +/- S.D.) to 1.41 +/- 0.67 (P less than 0.01), and returned to baseline values in 10 days (0.95 +/- 0.14). We conclude that Teflon injection into a paralyzed vocal cord creates a significant inspiratory airway obstruction that is reversible in 10 days.