Abstract: Development of a Medical Robot for Stereotactic Neurosurgery: Modelling, Simulation and Control Medical robotics seems to be a new trend in today's surgery. But although receiving much current attention, still very few systems are currently installed in operating theatres. Surgical robotics is still viewed with suspicion by many surgeons. One reason might be, that it is very expensive and appear often over complicated, on the other hand one particular "apparatus" can be used only for limited tasks. Another reason is the missing evidence of the postulated precision and a safe robotic operation and handling. These statements are especially true for stereotactic neurosurgery, where very high precision is demanded. Therefore the use of (image-guided) robots is reasonable. A team at our institution have started to develop a new manipulator system. The conception of such a system includes hard- and software-considerations. Further the geometric and mechanical relations of the system are modeled mathematically. The later means in particular the kinematics of the system and the calibration of modelling errors.