Direct kinematic observation was used to measure ratings of perceived exertion at the ventilatory breakpoint (RPE-Vpt) in 10- to 14-yr.-old girls (n=22) and boys (n=22). RPE for the overall body, legs, and chest were simultaneously estimated by a trained observer and self-rated by a subject during treadmill exercise using the Children's OMNI-Walk/Run Scale. Subjects' heart rate and oxygen consumption were measured during each minute of exercise. Vpt for the girls and boys, respectively, were 64.2 and 66.5% VO2 max. RPE-Vpt ranged from 6.0 to 6.5 Overall, 7.1 to 7.6 Legs, and 5.0 to 5.5 Chest for both the observation and self-rating procedures. Responses indicated (a) RPE-Vpt (Overall, Legs, Chest) did not differ (p>.05) between the observer and self-rating procedures and (b) Observer RPE-Vpt-Legs was greater (p<.05) than RPE-Vpt-Chest. Findings validated direct kinematic observation to code group-normalized RPE-Vpt for girls and boys performing treadmill exercise.