Acute obstruction of the upper airway from trachea, a foreign body or laryngospasm may lead to death in a few minutes. The immediate restoration of an adequate airway in these patients may be lifesaving. Spontaneous respiration by means of a needle inserted into the trachea was studied in 21 rabbits using 16, 18 and 20 gauge extracatheters. The results are as follows : 1) Airway resistance was markedly increased in all experimental animals, consequently tidal volume was also significantly decreased, but this seems to be compensatory by increased of respiratory frequency in 16G group. 2) Blood gas analysis revealed adequate pulmonary ventilation through the constricted airway (about 1/3 of normal sized trachea) during 60 minutes. In the other hand, hypercarbia, hypoxemia, and metabolic acidosis were developed in the group with severe constriction of the upper airway (about 1/4-1/6 of normal sized trachea). 3) The further study is postulated to confirm the possibility of application of needle tracheostomy in man, but the rabbits were tolerable to the constricted airway with a small sized needle (16G) into the trachea for 60 minutes.