Age-appropriate reinforcers have been found to be effective in promoting attentiveness and calmness with children with attention deficit hyperactivity disorder (ADHD). The present study with a 4-year-old ADHD boy found attentive calmness was substantially increased from a mean of about 3 seconds per trial to the maximum scheduled duration of 60 seconds by using a scheduled period of physical activity as the reinforcer for the attentive-calmness. These results suggest the possible use of this type of reinforcer as an addition or substitution for the usual reinforcers in contingency management with ADHD children. (Contains 1 figure.)