OBJECTIVE: To assess the effectiveness of a helium-oxygen mixture in reducing post-extubation stridor in children hospitalized for burns or trauma. DESIGN: Randomized, controlled crossover trial. SETTING: Harborview Medical Center's Burn and Trauma ICUs from March to September 1989. PATIENTS: Children less than 15 yr old who were electively extubated and had symptoms of postextubation stridor, but required less than or equal to 35% oxygen. INTERVENTION: Each treatment (helium-oxygen and oxygen-supplemented room air) was given in random order for 15 min after extubation. MEASUREMENTS: Respiratory distress was assessed by a physician blinded to treatment order using a standard stridor score and clinical judgment. RESULTS: There were 13 children with 15 extubations; seven (47%) of 15 patients required subsequent treatment with racemic epinephrine or reintubation. Stridor scores were lower with helium-oxygen than with oxygen-supplemented room air (2.8 vs. 3.7, p less than .005), and helium-oxygen was preferred in eight of nine trials in which one treatment was clearly favored by the physician. CONCLUSION: Because helium-oxygen therapy can reduce stridor scores and is clinically preferred by physicians caring for stridorous children, it may be a useful adjunctive therapy in pediatric trauma patients with postextubation stridor.