Stridor is noisy inspiration from turbulent gas flow in the upper airway. This chapter discusses the use of Heliox for temporarily treating stridor in the setting of ENT pathology. Stridor has many potential causes. It may occur as a result of foreign bodies, tumor formation, infections, subglottic stenosis, and airway edema, as well as a result of laryngomalacia, subglottic hemangioma, and vascular rings compressing the trachea. Stridor is usually diagnosed on the basis of symptoms and physical examination, with a view to revealing the underlying problem or condition. Chest and neck X-rays, CT scans, and/or MRIs may reveal structural pathology. Flexible fiberoptic bronchoscopy can also be very helpful, especially in assessing vocal cord function or in looking for signs of compression or infection. Heliox administered with a nonrebreathing face mask should be readily available in every operating room suite to assist in the treatment of stridor.