In this thesis, the dexterity of manipulators with rehabilitation applications is optimized in terms of manipulability. The optimal design is applied to non-redundant and redundant manipulators. For the non-redundant case, the manipulability improvement is realized by maximizing the link lengths of the manipulator. For the redundant case, the manipulability is maximized in terms of the optimal link lengths and optimal configurations using an exhaustive search. The design is fulfilled for healthy and faulty Jacobians. It is shown that the minimum degree of redundancy to apply fault-tolerant design is two. For the faulty case, the fault-tolerant relative manipulability is maximized, which shows how much dexterity is maintained in post fault conditions. The simulation results exhibit the effectiveness of the proposed configuration.