Corollary Discharge (CD) or efference copy is a copy of a motor command sent from a region of the brain that generates movements to another sensory or integrative region of the brain. In the monkey a CD circuit for saccadic eye movements extends from the superior colliculus through the medial dorsal nucleus of the thalamus to the frontal eye field. This talk considers the multiple uses of the CD in primates for control of sequential saccades, for perception and as a factor in schizophrenia. The CD was first established by seeing how it contributed to the guidance of saccadic eye movements. Subsequently, the contribution to perception was established, including its contribution to visual continuity across saccades. These methods used in monkey experiments have now been used by Thakkar and her collaborators to understand the possible role of CD in the sense of agency deficit found in schizophrenic patients. The final points considered are the relation of CD to schizophrenia and the contribution of CD studies to understanding the organization of MD thalamus in the transmission of internal signals within the brain to frontal cortex.