The study was designed to determine the strategies used by diplegic subjects to change walking speed. Two groups, limited community ambulators and community ambulators, were compared with controls to determine if ability to increase speed would decrease as a function of motor impairment. Compared with matched controls, diplegic subjects were slower and relied more on cadence to increase speed. The ability to change velocity and stride length was significantly less in the diplegic groups than in controls and accounted for the wider difference in their fast walking velocity. Velocity and stride length decreased, whereas stance time increased as a function of motor involvement. In the limited community ambulators, pelvic excursion was increased, whereas hip and knee excursion was reduced. By assessing fast speed, differences between controls and diplegic groups became more apparent.