This study examined the relationship between heart rate (HR) as a measure of physiological strain and ratings of perceived exertion (RPE) in 193 children (mean age= 11 yrs) and 188 adults (mean age =36 yrs) during submaximal cycle ergometry. Two methods of correlating HR and RPE were compared. Computing correlations (r) for each individual’s data and then taking the group mean produced very high rs, ranging from 0.92 to 0.95. Correlating HR and RPE for the entire group at all powers simultaneously produced much lower rs, ranging from 0.63 to 0.65. Correlations were essentially the same for children and adults, and there was no evidence of a practice effect. The results indicated that (a) children in this age group were as capable of expressing RPE as adults, and (b) absolute levels of perceived exertion were not predictive of physiological strain (as indicated by heart rate).