Computer-assisted therapy is one of the most promising new techniques for those suffering from physical and neurological dysfunction. Yet, impairments to physical movement arising from a central nervous system dysfunction or from muscle spasms generated through other neurological damage or dysfunction can often make it difficult or impossible for individuals to interact with computer-generated environments using a conventional mouse interface. This paper investigates the use of a 2-D haptic device as an assistive robotic aid to minimize the effects of the pathological absence of motor control in the upper limb in impaired users when using a mouse. The assistive functionality is evaluated in 2-D tracking tasks using a human subject with failure of the gross coordination of the upper limb muscle movements-“Muscle Ataxia.” The results demonstrate that with this system the capability of the impaired subject to track predefined trajectories within a computer generated 2D is significantly improved. The average of the means of the error distance for the trajectories performed under the assistive mode was significantly lower (more than 40%) than that of the trajectories without assistance. In addition, when using the assistive device, the impaired subject was able to complete the tracking tasks in less time.