Cognitive surgery is the vision of a surgeon being guided by assistance systems that not only perform preprogrammed tasks but understand a given situation, act on it and learn from it, similar to a human assistant. In a networked operating room, the operation room team must be linked to machines and processes by continuously recording and evaluating the course of treatment via sensors and medical devices. Based on that a context-aware assistance is realized, for example, intraoperative prediction of complications or robot-assisted camera guidance. Examples from research demonstrate the potential of such systems; however, this paradigm shift can only occur through interdisciplinary collaboration, where the requirements for cognitive assistance systems must be defined by surgeons in close cooperation with computer scientists and engineers. The surgeon should not be replaced but supported by cognitive assistance with the goal to improve patient care.