In young rabbits the growth of the subglottis was studied over a period of 20 weeks after interruption of the circularity of the cricoid on the ventral side. In all cases the cricoid developed into a U-like structure which did not cause an airway narrowing. However, a cricoid lesion combined with an injury to the soft tissue lining led up to a subglottic stenosis. It was concluded that when the soft tissue layer is undamaged, an intact circular structure of the cricoid is not compulsory for the normal development of the subglottis.