Intrathecal baclofen withdrawal syndrome is a known complication of intrathecal baclofen pumps. Its origin is postulated as an independent form of a serotonergic syndrome occurring from loss of gamma-aminobutyric acid B receptor-mediated inhibition of serotonin. Prodromal symptoms include pruritus, a return of deep tendon reflexes, and increased spastic hypertonia. Previous reports have documented use of cyproheptadine in treatment of this syndrome in adults with positive results. We present the case of a 14-yr-old child with cerebral palsy who developed pruritus and worsening spastic hypertonia 18 mos after pump implantation. She had been previously treated with 520 microg/day of intrathecal baclofen. Progression of her symptoms was successfully arrested by the administration of both oral and intrathecal baclofen and 6 mg of oral cyproheptadine every 6 hrs for 1 day. We postulate that cyproheptadine should be considered a valuable adjuvant therapy for treatment of suspected intrathecal baclofen withdrawal syndrome.