AIM To describe the heart rate (HR) and heart rate variability at rest, during a submaximal treadmill test and at rest posttreadmill in children with cerebral palsy (CP). METHODS Twenty children (6-11 years) with CP participated, who had Gross Motor Function Classification System levels I to III. The HR was monitored for 5 minutes seated, during a submaximal treadmill test, and after 5 minutes rest posttreadmill. Outcome variables were HR and the square root of the mean squared differences of successive differences between adjacent heart beats (RMSSD). RESULTS HR increased during the last stage of the treadmill test compared with rest. RMSSD was reduced during the last 2 minutes of the treadmill test compared with rest. The HR and RMSSD mean value at the second minute posttest were not significantly different from the pretreadmill rest value. INTERPRETATION The cardiac system in children with CP responded to the submaximal testing.