This thesis addresses the problem of robust position and force control of robot manipulators. Sliding mode control methodology is used to develop the position/force control schemes which are robust against internal and external dynamic disturbances. Four control laws, including a unified control law, are developed in this thesis. Based on the reduced order model, two sliding mode based force control schemes are developed in joint space. Using hybrid control strategy and hierarchical control method, a task space position/force control scheme is developed. A unified controller is also proposed in task space for free motion, impedance, position/force and impedance/force control. A modified saturation function is proposed to accelerate the convergence of sliding mode transition phase and eliminate the control chattering. By using the proposed control schemes, a satisfying performance can be achieved by using the knowledge of the upper bound of dynamic disturbances.