Constraint-Induced Movement Therapy or CI Therapy is an approach to physical rehabilitation elaborated from basic neuroscience and behavioral research with primates. The application of the CI therapy protocol to humans began with the upper-extremity after stroke and was then modified and extended to cerebral palsy in young children, traumatic brain injury, and multiple sclerosis. A form of CI therapy was developed for the lower extremities and has been used effectively after stroke, spinal cord injury, fractured hip, multiple sclerosis, and cerebral palsy. Adaptations of the CI therapy paradigm have also been developed for aphasia (CI Aphasia Therapy or CIAT), focal hand dystonia in musicians, and phantom limb pain. The range of these applications indicates that CI therapy is not only a treatment for stroke, which is its most common application, but for overcoming learned nonuse in general, a phenomenon which manifests as excess disability after different types of CNS injury which until now have been largely refractory to treatment. CI therapy in all of its forms consists of four major components: 1) intensive training of an impaired function for several hours a day for multiple days, 2) training by the behavioral technique termed shaping, 3) a set of behavioral techniques, the transfer package, designed to transfer gains from the treatment setting to daily activities in the life situation, and 4) "constraining? or discouraging compensatory patterns of movement developed in the early post-injury period to substitute for loss of function. CI therapy for the upper-extremity in adults and children has been shown to produce an increase in the volume of grey matter in motor areas of the brain and there is evidence that CI Aphasia Therapy has a similar effect in language-related regions.