<p>The effects of masking on the localization of a moving signal in the vertical plane were studied. A stationary masker was located above the subject’s head, and the stimulus moved from 8° to 42° upward toward the masker or downward away from it. Masking effects were assessed by varying the delay between the masker and the stimulus within the range 0–200 msec, with an additional delay of 1200 msec. At delays of up to 80 msec, sound image (SI) localization was alternative: either near the masker or at the moving stimulus. As the delay increased, the probability that the SI would be localized near the masker decreased, while the probability of localization near the stimulus increased. As the delay increased, the trajectory of the SI expanded, though it did not reach the control value in the quiet. The main factor narrowing the trajectory of the SI was displacement of its starting point in the direction of motion. The perceived position of the masker was displaced toward the presentation of the moving stimulus. The signal was detected most effectively when the stimulus moved away from the masker. Comparative analysis showed worse discrimination of a moving sound source during masking in the vertical plane as compared with masking in the horizontal plane.</p>