Hippotherapy (HPOT) is a therapy that uses horse movement. This pilot investigation objectively evaluated the efficacy of HPOT in improving head/trunk stability in children with cerebral palsy (CP). The participants were six children with spastic diplegia and six children without disability. Head and trunk stability was challenged by using a motorized barrel and measured by a video motion capture system before and after a 12-week intervention of 45 min of HPOT a week. The variables measured were anterior-posterior (AP) translation of the head, and spine at five points and average AP head angles. At pre-testing, children with CP demonstrated significant differences in AP translation and AP head rotation compared with children without disability. Following HPOT, children with CP demonstrated significant reductions in head rotation and AP translation at C7, eye, and vertex. At post-testing, translation at C7 did not differ significantly between children with CP and children without disability. After HPOT intervention, children with CP reduced their AP head rotation and translation, suggesting that they had increased stability of the head and trunk in response to perturbations at the pelvis. The findings suggest that HPOT might improve head and trunk stability in children with CP. (Contains 1 table and 9 figures.)