A therapeutic approach to rehabilitation of movement after stroke, termed constraint-induced (CI) movement therapy, has been derived from basic research with monkeys given somatosensory deafferentation. CI therapy consists of a family of therapies; their common element is that they induce persons with stroke to greatly increase the use of a more-affected upper extremity (UE) for many hours a day over a 2- to 3-week period. These therapies have significantly improved quality of movement and substantially increased amount of use of a more-affected UE in the activities of daily living in life situations. A number of neuroimaging and transcranial magnetic stimulation studies have shown that the massed practice of CI therapy produces a massive use-dependent cortical reorganization that increases the area of cortex involved in the innervation of movement of the more-affected UE. The intensity and schedule of delivery of this very efficacious therapy is quite different from that of more traditional physical rehabilitation approaches. As a result, to be clinically applicable, the CI therapy approach to rehabilitation will likely require a paradigm shift in the delivery of physical rehabilitation services.