The question under consideration was does cardiorespiratory training improve aerobic fitness in children with cerebral palsy and is there any carryover into activity? The study design consisted of a systematic review of randomized trials using the Cochrane Collaboration guidelines. Participants were children of school age with cerebral palsy. Intervention included cardiorespiratory training consisting of activities conducted for an extended period, which were progressed in terms of duration and/or intensity over time. Combination programs were included if cardiorespiratory training comprised at least half of the program. Outcomes had to include a measure of aerobic fitness, for example, peak oxygen uptake. In addition, measures of activity that reflect aerobic fitness, for example, 6-min Walk Test were also desirable. Three studies were identified which randomized participants to cardiorespiratory training or no intervention in addition to usual physiotherapy. A meta-analysis was not performed because of lack of data. Therefore, the between-group differences are reported in terms of percentage benefit. Short-term cardiorespiratory training (i.e. 2-4 months) increased aerobic fitness by 18-22% and long-term training (i.e. 8-9 months) by 26-41% compared with no additional intervention. Short-term training (i.e. 2-4 months) increased activity by 0-13%, and long-term training (i.e. 8-9 months) by 2-9%. The conclusion is that there is limited evidence about the effect of cardiorespiratory training in children with cerebral palsy. The available evidence suggests that training may improve aerobic fitness, but that there is little carryover into activity.