AIMS: To measure heart rate (HR) and heart rate variability (HRV) at rest, during and after walking among children with cerebral palsy (CP) as compared to age matched typically developed (TD) controls. The second aim was to describe the association between HRV and motor performance in children with CP. METHODS: Twenty six children with CP (age 8-14 years) and sixteen TD children matched for age assessed during rest, walking and after walking. HR and HRV parameters include: time domain parameters: standard deviation of the R-R interval (SDNN), square root of the mean squared differences of successive R-R differences (RMSSD). RESULTS: Children with CP demonstrated higher mean HR values at rest; 98.4 +/- 13.9 bpm vs 83.0 +/- 11.5 bpm in controls, (p < 0.05) and significantly lower time domain measures of HRV; RMSSD was 52.0 +/- 19.1 ms and 87.0 +/- 39.8 ms respectively (p < 0.05). Significant interaction effects were noted for HR and time domain HRV parameters. HR increased and SDNN and RMSSD decreased when children change their activity level from rest to walking and HR decreased and SDNN and RMSSD increased again after walking for TD children but not for children with CP (p < 0.05). No association was noted between HRV and motor performance in children with CP. INTERPRETATION: The findings of this study suggest that among children with CP, the cardiac autonomic mechanism is less efficient at rest and less adaptive to exercise and activity as compared to TD children.