The influence of exercise-induced arousal on the processing of visual information by three age groups was tested. Subjects were required to perform the Treisman visual detection task both at rest and during a steady-state walk at 75% of their maximum heart rate. The expected age differences in perceptual performance were apparent. The detection performance of 8-year-olds was poorer than that of 11-year-olds and adults. Detection of conjoined feature targets, with increases in the array size, showed a decrement in comparison to single feature targets. Subjects responded more quickly at all levels of distraction when a target was present while they were exercising. The results supported certain elements of Treisman's feature integration theory. This study has provided evidence that an exercise stress equivalent to 75 % of maximum heart rate had a positive effect on the visual perceptual performance of all groups tested. Both array size and feature conditions interacted with age. This suggests that children are not able to avoid irrelevant information as effectively as adults. In addition, children are differentially affected by different target characteristics in the detection task.