Entraining human gait with periodic torque from a robot may provide a novel approach to robot-aided walking therapy that is competent to exploit the natural oscillating dynamics of human walking. To test the feasibility of this strategy we applied a periodic ankle torque to neurologically impaired patients (one with stroke and one with multiple sclerosis). As observed in normal human walking, both patients adapted their gait periods to synchronize with the perturbation by phase-locking the robotic torque at terminal stance phase. In addition, their gait cadence became significantly faster due to the training with clear after effects when the perturbation ceased. These results support a new strategy for walking therapy that exploits an embedded neural oscillator interacting with peripheral mechanics and the resulting natural dynamics of walking, which are essential but hitherto neglected elements of walking therapy.