A 28-year-old woman in status asthmaticus and respiratory acidemia refused orotracheal intubation and mechanical ventilation in the emergency department. In view of this situation, a mixture of helium-oxygen gas (heliox) was initiated with a nonrebreathing oxygen mask. Within 2 hours of treatment, the patient's respiratory acidemia had been corrected, and heliox inhalation therapy was discontinued without further incident.