This study examined the validity and reliability of the Rating of Perceived Exertion (RPE) scale and the Children's Effort Rating Table (CERT) as methods of regulating exercise intensity during discontinuous cycle ergometry. Sixty-four school children (ages 9-10) were randomly assigned to one of two groups, RPE or CERT, and received two trials 7 days apart. On both occasions, subjects produced 4 x 4-min scale-specific exercise intensities-3, 5, 7, and 9 (CERT) or 8, 12, 15, and 18 (RPE)-interspersed with 2-min rest periods. Analyses yielded significant (p<.01) correlations between perceived effort levels and objective measures: r=.47 to .61 (heart rate) and r=.59 to .75 (power output). Intraclass correlations indicated satisfactory overall repeatability of the produced exercise intensities (R>.70), but some notable inconsistencies were observed. The usefulness of effort perception scales among preadolescent children is presently rather limited, probably due to a number of confounding factors that need to be systematically addressed.