TREIBER, F. A., L. MUSANTE, S. HARTDAGAN, M. LEVY, and W. B. STRONG. Validation of a heart rate monitor with children in laboratory and field settings.Med. Sci. Sports Exerc., Vol. 21, No. 3, pp. 338–342, 1989. The validity of the Sport Tester PE 3000 portable heart rate monitor for use with children was assessed by comparing readings with simultaneously recorded ECG heart rates in three studies, two using laboratory tasks and one in a field setting. Study 1 examined the validity of the Sport Tester with a sample often 10-yr-olds performing a cycle ergometer exercise task. Sport Tester readings taken during three 3-min exercise loads were correlated from 0.97 to 0.99 with simultaneously recorded ECG heart rates. In study 2, 23 children from 4 to 6 yr of age performed treadmill exercise for three 1-min intervals while Sport Tester and ECG heart rate data were obtained. Correlations for the three intervals ranged from 0.94 to 0.99. Study 3 obtained ECG and Sport Tester heart rates in 14 7− to 9-yr-olds who engaged in 3-min periods of standing, walking, jogging, throwing a ball, batting a ball, and playing on a jungle gym. Significant correlations of at least 0.98 between Sport Tester and ECG heart rates were obtained during all six activities. For all three studies, standard errors of estimate were low, ranging from 1.1 to 3.7 beats·min-1. For individuals, maximum differences ranged from 0 to 12.4 beats·min-1. Collectively, these findings indicate that the Sport Tester provides valid readings of young children's heart rates across a wide range of exercise involving upper- and lower-body movements.