Surgeons need assistance in most types of surgery. This necessary teamwork is costly and can be a source of error and inefficiency due to communication problems such as a lack of coherence among the surgeon’s and assistants’ actions. A robotic arm under the surgeon’s full control improves his/her dexterity and simplifies the teamwork. While the hardware of such an arm is readily available, the most efficient way to use it remains an open question. This chapter presents our experimental setup and paradigm for studying the control of a third arm for the surgeon. This study mainly focuses on the embodiment mechanism of the third arm, the intuitiveness of the control strategy and the appropriate level of complexity of the tasks.