Objective: To investigate whether training in a virtual environment with a haptic device will improve motor function in the left hemiparetic arm of a stroke subject. Design: Single case, A-B-A design. Setting: University hospital research laboratory. Participant: A man in his late fifties (right handed), with a right-hemisphere lesion that caused a deficit in the left upper extremity. Intervention: The subject trained with a 3-dimensional computer game during a 4-week period that consisted of twelve 90-minute sessions. Main Outcome Measures: Three tests (Purdue pegboard test, dynamometer hand-grip strength, upper-extremity test) and a subjective interview were used to evaluate motor performance. Results: Improvements were found in fine manual dexterity, grip force, and motor control of the affected upper extremity. The subject reported that there was a change in his day-to-day use of the upper extremity and that he was able to use it in activities that were previously impossible for him. Conclusions: Training with virtual reality and haptics can promote motor rehabilitation. (C) 2004 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation.