Abstract. The aim of this study was to make use of a pr eviously introduced method of a simulated tripping perturbation to examine stability of walking in individuals with and with out cerebral palsy. This tripping perturbation is a forward-dynamics analys is, and it works so that in a subjec t-specific muscle-driven simulation of walking, created from experimental gait data, a force is applied to the swin g-foot, and resulting changes in the kinematics are observed. Here, changes in the fore-aft position of the trunk were analyzed. Subjects were 10 children with spastic diplegic cerebral palsy and eight un impaired children walking at their self-sel ected speed. Several tripping perturbations throughout the swing phase were performed, and each perturbation was used to analyze stability at a respective instant of time. At a given instant of time, walking was defined as stable if after initially deviating from its unpertur bed position, because of the pertur bation, the trunk then approached and stayed close to that position. Walking was in turn de fined as unstable if the trunk moved away from its unperturbed position. All unimpaired subjects were stable at some point of their swi ng phases, wherea s six out of the ten CP subjects were never stable. The unimpaired subjects we re statistically signific antly stable for a larger percentage of the swing phase t han the CP subjects (p < 0. 05). On the average, unimpaired subjects were stable for 8.5% of the swing phase while CP subjects were st able for 1.5% of the sw ing phase. These findings demonstrate that a tripping perturbation is capable of detecting a balance impa irment. Thus, it shows promise as a tool for rehabilitation.