Robotic systems will play a critical role in the on-orbit assembly, external maintenance and operations of the International Space Station. This paper reviews the mission and tasks to be performed by the external robotic devices on the Station and provides an overview of the design of the mobile servicing system for the Station. The mobile servicing system represents the state-of-the-art in operational space robotics and features a large manipulator system and smaller dexterous manipulators in order to fulfil its functions. The paper focuses on the driving performance requirements, major mechanical design features, and the control systems of the mobile servicing system, including advanced features such as vision systems.