This study compared the accuracy of heart rate monitoring, pedometry, and uniaxial and triaxial accelerometry for estimating oxygen consumption during a range of activities in Hong Kong Chinese boys. Twenty-one boys, aged 8-10 years, walked and ran on a treadmill, played catch, played hopscotch, and sat and crayoned. Heart rate, uniaxial and triaxial accelerometry counts, pedometry counts, and scaled oxygen uptake (SVO2) were measured. All measures correlated significantly with VO2 scaled to body mass-0.75 (SVO2). The best predictor of SVO2 was triaxial accelerometry (R2 = 0.89). Correlations in this study were comparable with those in a previous study that used identical methods on 30 UK boys and girls. These results provide further confirmation that triaxial accelerometry provides the best assessment of energy expenditure and that pedometry offers potential for large population studies. Copyright © 1999 Human Kinetics Publishers, Inc.