This study described the aerobic capacity [VO[subscript 2peak] (ml/kg/min)] in contemporary children and adolescents with cerebral palsy (CP) using a maximal exercise test protocol. Twenty-four children and adolescents with CP classified at Gross Motor Functional Classification Scale (GMFCS) level I or level II and 336 typically developing children were included. All children performed a progressive exercise test on a treadmill with respiratory gas-exchange analysis. The results are compared with normative values for age and gender-matched controls. Aerobic capacity of children and adolescents with CP, who are classified at GMFCS level I or II was significantly lower than that of typically developing controls. Especially in girls with CP, the aerobic capacity deteriorated with age. The aerobic capacity of contemporary children and adolescents with CP, who are classified at GMFCS level I or II is significantly lower than that of typically developing controls. (Contains 1 figure and 3 tables.)