This article reviews a decade of work aimed at developing effective interactive robotic tools to treat and understand motor impairment and disability. The success of an initial pilot study with acute-phase in-patients recovering from stroke prompted a larger study showing that these results could be replicated and a follow-up study showing that the benefits lasted. Studies of chronic-phase out-patients demonstrated that similar benefits could be obtained which also lasted and were accompanied by a concomitant reduction of pain. Exploration of the likely biology of recovery suggested an improvement of robotic treatment in the form of performance-based progressive therapy aimed at accelerating a process akin to motor learning postulated to underlie recovery. Initial studies of this method show a dramatic improvement over the previous successes. Kinematic studies of the recovery process show that, similar to the development of motor behavior in infants, it begins with stereotyped submovements and proceeds by progressively merging these to approach unimpaired motor performance.