Hand/eye calibration is useful in many industrial applications, for instance, grasping objects or reconstructing 3D scenes. The calibration of robot systems with a visual sensor is essentially the calibration of a robot, a sensor, and hand-to-eye relation. This paper describes a new technique for computing 3D position and orientation of a 3D visual sensor system relative to the end effector of a robot manipulator in an eye-on-hand robot configuration. When the position of feature points on a calibration target in sensor coordinates viewed at each robot movement, and the position of these points in world coordinates and the relative robot movement between two robot motions are known, a homogeneous equation of the form AX equals XB can be derived. To obtain the unique solution of X, it is necessary to make two relative robot arm movements and to form a system of two equations of the form: A1X equals XB1 and A2X equals XB2. In this paper, a closed-form solution of this calibration system is derived, and the constraints for existence of a unique solution are described in detail. Test results obtained through a series of simulation show that this technique is a simple, efficient, and accurate method for hand/eye calibration.