There has been a rapid increase in the past decade in the number of robotic devices that are being developed to assist in movement rehabilitation of the upper extremity following stroke. Many of these devices have produced positive clinical results. Yet, it is still not well understood how these devices enhance movement recovery, and whether they have inherent therapeutic value that can be attributed to their robotic properties per se. This chapter reviews the history of robotic assistance for upper extremity training after stroke and the current state of the field. Future advances in the field will likely be driven by scientific studies focused on defining the behavioral factors that influence motor plasticity.