Twenty overweight children, ages 9-15 years, participated in a study on the usefulness of the Borg 6-20 perceived exertion (RPE) scale as a means for exercise prescription. As a criterion measure, they cycled at four intensities, based on pre-determined % peak power, giving RPE ratings at each load. During two return visits subjects were asked to set the resistance on the ergometer (cycle tasks) and to walk or run around an oval track (track tasks) at intensities they perceived as RPE = 7, 10, 13 and 16. HR-on-RPE regressions were compared among the criterion, cycle and track tasks. Cycle and track lines differed from the criterion (p less than .001). Subjects were, however, able to discriminate among each of the RPE prescriptions on the cycle. They overestimated intensities on the track tasks. We conclude that overweight children need additional instruction in using the Borg scale for exercise prescription.