There exists a widespread tendency to place the blame for a respiratory abnormality of any magnitude in infancy on the thymus gland, particularly if there is x-ray evidence of thymic enlargement. In the absence of x-ray evidence it is often assumed, as pointed out by Wasson,1that the roentgenogram did not accurately portray the situation, and the thymus still may be believed to be the cause of the symptoms. It is not our purpose to review or to evaluate current opinion on thymic enlargement or so-called status thymicolymphaticus. We have been impressed, however, by the apparent confusion of congenital laryngeal stridor with thymic disease as indicated by the fact that in the past three years almost all infants in whom we have established the diagnosis of congenital laryngeal stridor had been referred to us with the diagnosis of enlarged thymus. This paper thus has been prompted by an experience