Veterans and other Americans who survive stroke often face disabling motor impairments that impede performance of activities of daily living and limit free-living activity. Prominent among these are diminished walking and balance functions, which not only foster a sedentary lifestyle and physical deconditioning, but also increase the risk of injuries due to falls. Recent research has demonstrated how motor learning based interventions can modify brain activity and improve motor functions in persons with stroke. Now there is a major research opportunity to advance the effectiveness of these interventions by applying new robotics technologies to improve control of essential functions such as gait and balance. One critical area for performance of walking and standing balance is the control of the ankles, as they are a major conduit of mechanical power in gait and also modulate torques affecting the motion of the whole body center of mass when balancing. Thus the current proposal is designed to investigate two approaches for using an impedance controlled ankle robot to improve gait and balance among stroke survivors with chronic lower extremity weakness. One approach uses the ankle robot in a seated visuomotor training program that focuses has subjects play video games with the weaker ankle to improve paretic ankle motor control that may carry over to gait and balance functions. The other approach uses task-specific gait training by integrating use of the ankle robot during treadmill exercise training to assess effects on the same functions. The effectiveness of both robotics approaches will be compared to that of a treadmill exercise program without robotics.