Objective: To determine if the continuous intrathecal delivery of baclofen will control spastic hypertonia caused by long-standing cerebral palsy (CP). Design: Case series. Setting: Tertiary care outpatient and inpatient rehabilitation center directly attached to a university hospital. Patients: Thirteen CP patients (average age, 25 yr; range, 13-43 yr) with intractable spastic hypertonia and quadriparesis (one of whom had predominate diplegia) who had not responded to oral medications including baclofen. Intervention: Patients were screened via a bolus injection of haclofen intrathecally. Those who dropped an average of 2 points on their lower extremity (LE) Ashworth scores were offered computer-controlled pump implantation for 12 months of continuous delivery of intrathecal baclofen (ITB). Main Outcome Measures: Ashworth rigidity scores, spasm scores, and deep tendon reflex scores were collected for both the upper extremities (UEs) and LEs. Differences over time were assessed via descriptive statistics and Wilcoxon's signed-rank test. Results: After 1 year of continuous ITB treatment, the average LE Ashworth score ± standard deviation decreased from 3.4 ± 1.2 to 1.5 ± 0.7 (p < .0001), spasm score from 1.4 ± 1.6 to 0.6 ± 1.2 (p = .1024), and reflex score from 2.5 ± 1.2 to 0.7 ± 1.1 (p < .0001). The average UE Ashworth score decreased from 3.0 ± 1.2 to 1.7 ± 1.0 (p < .0001), spasm score from 1.2 ± 1,6 to 0.2 ± 0.6 (p = .0135), and reflex score from 2.3 ± 0.7 to 0.5 ± 0.9 (p < .0001). The average ITB dose required to attain these effects at 1 year was 263 ± 91 μg continuously infused per day. Conclusion: Continuously infused ITB can reduce spastic hypertonia in the UEs and LEs associated with long-standing CP. This reduction in tone will allow more freedom of movement and the potential for improved function.