Background and Purpose - We sought to determine whether continuous intrathecal delivery of baclofen can effectively decrease spastic hypertonia due to stroke. Methods - Stroke patients with >6 months of intractable spasticity were screened via a randomized, double-blind, placebo-controlled crossover design of either intrathecal normal saline or 50 μg baclofen. Those who dropped an average of 2 points in either their affected lower extremity side Ashworth or Penn spasm frequency scores were then offered computer-controlled pump implantation for continuous ITB and followed prospectively for up to 12 months. Results - In 21 stroke patients 6 hours after the active drug bolus, the average (±SD) lower extremity Ashworth score on the affected extremities decreased from 3.3±1.2 to 1.4±0.7 (P<0.0001), spasm score from 1.2±1.2 to 0.1±0.3 (P=0.0224), and reflex score from 2.1±1.2 to 0.1±0.5 (P<0.0001). The average upper extremity Ashworth score on the affected extremities decreased from 2.8±1.1 to 1.8±0.8 (P<0.0001), spasm score from 0.7±1.0 to 0.2±0.4 (P=0.1544), and reflex score from 2.1±0.9 to 1.2±0.9 (P=0.0004). All active drug scores were statistically different from placebo scores at 6 hours (P<0.05). With up to 12 months of continuous infusion of ITB in 17 implanted patients, the average lower extremity Ashworth score on the affected extremities decreased from 3.7±1.0 to 1.8±1.1 (P<0.0001), the spasm score dropped from 1.2±1.3 to 0.6±1.0 (P=0.4282), and the reflex score decreased from 2.4±1.3 to 1.0±1.3 (P<0.0001). The average upper extremity Ashworth score in the affected extremities decreased from 3.2±1.1 to 1.8±0.9 (P<0.0001), the spasm score dropped from 0.7±1.0 to 0.3±0.8 (P=0.8685), and the reflex score decreased from 2.4±0.8 to 1.5±1.2 (P=0.3337). The average continuous ITB dose required to attain these effects was 268 μg/d. Conclusions - Intrathecal infusion of baclofen is capable of maintaining a reduction in the spastic hypertonia resulting from stroke.