The authors review the main technical issues in computer-integrated surgery (CIS) systems. They illustrate with examples of working systems the state of the art in the field and provide perspectives on deployment and future developments. They discuss the structure of CIS systems. At the core is a computer (or network of computers) running various modeling and analysis processes, including image and sensor processing, creation and manipulation of patient-specific anatomical models, surgical planning, visualization, monitoring, and control of surgical processes. After receiving information about the patient from medical imaging devices, some CIS systems act directly on the patient using specialized robots or other computer controlled therapy devices.