Motion-in-depth refers to a movement towards or away from an observer. The detection of motion-in-depth, the discrimination of its direction (i.e., towards or away), and the estimation of its speed are crucial for our survival. For example, judging the speed and direction of a ball coming towards us when playing, e.g., tennis, detecting the deceleration of the car driving in front of us, or predicting whether we will make it across the tracks before being hit by an approaching train, all these tasks require the reliable and accurate perception of motion-in-depth.When an object moves towards or away from us, the images it projects on the retinas of the two eyes vary systematically with the movement. These variations can be used by the visual system to detect both the direction and speed of motion in depth. Some of these changes can be detected with only one eye (monocular cues). For example, when objects move towards or away from an observer, the size of the retinal images changes (looming): the size increases when the object approaches and decreases when it recedes. Other systematic variations are only detected by comparing the retinal images of the left and the right eye (binocular cues). For example, for a point moving directly towards an observer in depth, the corresponding points in the retinal images move in opposite directions in the two eyes. Both monocular and binocular cues contribute to the perception of motion-in-depth in the real world. However, to study each cue and the mechanisms underlying the processing of the cue separately, stimuli can be created that contain only one type of information. Here, we will be only concerned with the different types of binocular cues to motion-in-depth and will not consider the looming cue.