A systematic investigation was conducted during the process of anoxic death in newborn pups, rabbits and kittens less than 24 hr. old. Simultaneous measurements of respiration, heart rate and blood pressure were made. Considerable individual variation in the respiratory responses of newborn animals breathing nitrogen was noted. Under hypoxic conditions, respiratory failure may follow circulatory failure in the adult, whereas in the newborn, respiratory failure always occurred long before circulatory failure. The effect of anoxia on the cardiovascular system of the newborn at the time of the last breath was not as pronounced as might have been anticipated. Great individual differences with respect to blood pressure and heart rate throughout the period of anoxia were noted. The systolic blood pressure, on the average, was seen initially to fall more rapidly than the diastolic blood pressure or heart rate; it then slowly tapered off. The circulatory system was noted to function, although at hypotensive levels, for long periods of anoxia. Submitted on June 29, 1959