Idiopathic subglottic stenosis (iSGS) is a rare and life-threatening disease involving airway obstruction. Given its rarity, a number of options for treatment have been developed. The proposed study will continue and extend the PCORI-funded study in iSGS conducted by the North American Airway Collaborative (NoAAC) to collect objective long-term data on outcomes and side effects. This information is critical to help patients decide on the best treatment.