OBJECTIVE: To determine the efficacy of forced-use therapy (FUT) on the improvement of upper-extremity function in children with hemiplegic cerebral palsy (CP). DESIGN: Prospective case series. SETTING: Outpatient ambulatory clinic in South Korea. PARTICIPANTS: Thirty-one patients with hemiplegic CP were assigned to the FUT group (n=18) or to the control group (n=13). The mean age of the patients in the FUT group was 33.2 months and in the control group it was 43.2 months. INTERVENTIONS: The FUT group wore a short-arm Scotchcast on the unaffected arm for 6 weeks and also participated in a conventional rehabilitation program that included stretching exercises and functional occupational therapy for the upper extremity. The control group underwent the conventional rehabilitation program only. MAIN OUTCOME MEASURE: Hand function tests, including the box and block test (BBT), Erhardt Developmental Prehension Assessment (EDPA), and WeeFIM instrument taken before and after 6 weeks of treatment. RESULTS: Before treatment, there was no significant difference between groups in the BBT, EDPA, and WeeFIM scores. After 6 weeks of treatment, however, the FUT group showed significant improvement in the affected arm in the BBT and EDPA scores, compared with the control group (P<.05). The self-care score on the WeeFIM was also significantly improved in the FUT group (P<.05). CONCLUSIONS: FUT combined with a conventional rehabilitation program appears to be more effective than a rehabilitation program alone in improving affected hand function in children with hemiplegic CP.