Aim 1: to test the efficacy of 3 different constraint conditions used as part of administering a standardized form of therapy known as ACQUIRE (DeLuca, Echols, & Ramey, 2007). The 3 constraint conditions are: i) continuous constraint, ii) part-time constraint, and iii) no constraint. In all 3 groups, children will receive 3 hours of therapy per day for 5 days per week for 4 consecutive days. Therapy is delivered by licensed occupation or physical therapists who have been trained to deliver ACQUIRE therapy to high fidelity. In addition, parents are trained to provide one hour of practice in their homes, using techniques compatible with those used by the ACQUIRE therapist. Efficacy will be measured primarily by changes in the children's assessed skill levels in using their upper extremities, both the hemiparetic (affected) and the non-hemiparetic (less involved) upper extremities, used alone and together (i.e., in completing bimanual tasks). In addition, changes in brain functioning related to receiving the 3 different constraint conditions will be measured using functional Near-Infrared Spectroscopy (fNIRS), a non-invasive and safe procedure that permits children to be active while recording takes place.