Several unresolved issues in stereopsis are discussed that are related to the visual processing of dynamic disparity information. These unresolved issues include: (1) how well does the visual system compute temporal change in disparity and what kind of computation is used; (2) what is the neurophysiological basis of such processing in humans; and (3) how is the information gleaned from such processing used for guiding human action. The resolution of these issues will likely involve an adoption of a philosophical perspective in which dynamic disparity is viewed as playing an important role in the control of behavior and in which stereopsis is studied within the context of control-systems analysis.