Nine children with spastic cerebral palsy (CP) and 9 controls (mean age 13.5 and 14.0, respectively) completed a maximal walking test on the treadmill. Initial gradient was set at 0% with a speed increase every 2 minutes until the “fastest walking speed” was achieved in the third stage. The gradient was then increased by 2.5–5% every 2 minutes. V̇O2max of the CP children was significantly lower (p = .001) than that of the controls (32.7 vs. 45.2 ml · kg1 · min−1). There was no significant difference in maximal heart rate between the two groups (189 vs. 197). However, the CP subjects had significantly higher (p = .007) ventilatory equivalent for O2 compared to the controls (41.4 vs. 33.6). The lower V̇O2max values of the CP children might reflect inefficient ventilation, compromised circulation, and local fatigue in the spastic limb muscles.