One hundred-and-fifty-five neonates and infants up to the sixth month of postnatal age were investigated to reveal the cause of clinically relevant stridor. In 100 patients congenital stridor was found, in 55 children the stridor was considered to be acquired. A curled, soft epiglottis, almost synonymously used with the diagnosis of congenital stridor, was found in 7% only, indicating different methods of investigation and different selection of patients compared to previous years. In acquired stridor the majority of infants showed laryngeal and tracheal trauma, mostly due to the use of too large tracheal tubes.