OBJECTIVE To explore the effect of mitomycin treatment on the pediatric airway following laryngotracheal reconstruction. METHODS Randomized, double-blind, placebo-controlled trial. METHODS Children aged 2 to 17 years with subglottic or upper tracheal stenosis undergoing laryngotracheal reconstruction at a single, tertiary care, children's hospital. METHODS At the time of extubation or stent removal, the children underwent bronchoscopy and 0.4 mg/mL (2 mL of a 0.2-mg/mL solution of either mitomycin or an equal volume of isotonic sodium chloride was directly applied to the subglottic region for a single application of 2 minutes. These children then underwent interval endoscopy at 2 weeks, 6 weeks, and 3 months postoperatively for assessment of their airways. RESULTS Granulation tissue was graded on a scale of 0 (none) to 4 (near-total or total occlusion). Videotapes of endoscopies were independently observed and graded by 3 pediatric otolaryngology fellows with a subsequent interobserver agreement of 91.6%. The results were then dichotomized to represent a single cohort in which further surgical intervention would be required and another separate cohort in which further surgery would not be required. At the 1-year mark, interim analysis was performed by a Data Safety and Monitoring Committee. At this time, 13 children had been randomized to the mitomycin-treated arm of the study and 11 children to the placebo-treated arm. A 2-tailed Fisher exact test revealed a value of 1.00. The Data Monitoring and Safety Committee advised that the trial should be stopped because the distributions between the 2 populations were almost identical. CONCLUSIONS We cannot reject the null hypothesis that a single topical dose of mitomycin exerts an equal benefit as does isotonic sodium chloride when applied to the pediatric airway after laryngotracheal reconstruction.