The influence of rhythmical rectilinear vertical movements and of pitching movements upon respiration was studied in dogs and cats. Both types of movements induced an increase in frequency and amplitude of respiration. The effect is often most marked in the beginning of the movements, sometimes slow waves of increase and decrease in amplitude appear. The effect may outlast the stimulation, or may be followed by a period of inhibition (diminished amplitude of the resp. movements). In superficial anesthesia first the increase in the rate of respiration is affected, while the increase in amplitude during the vertical movements is still present. Deep anesthesia completely abolishes the reaction. After extirpation of the cerebral hemispheres, the thalami, and the hypothalamus, the various types of the reaction could still be observed; if the reactivity of the resp. center was depressed, sometimes an inhibitory reaction appeared. It is concluded that the resp. reactions on vertical movements are at least partly due to brain stem reflexes. An analysis of the importance of the various receptors in this reaction by extirpation expts. showed that mainly impulses from the labyrinth and from the area of the spinal nerves participate in producing the respiratory reactions upon vertical movements, while retinal impulses play only an accessory part. These resp. reactions appear independently of reactions of the vasomotor and digestive apparatus.