Recently an anatomic model was reported for adults that standardized the platform height for step tests using an individual's stature and a specified hip angle. In order to determine if the model could be used to predict the platform height for children, platform heights were calculated and hip angles were measured in 146 boys and 140 girls ages 6 to 18 years who were divided into four age groups (6 to 8, 9 to 11, 12 to 15, and 16 to 18 years old). There were no statistical differences between measured and calculated hip angles in any of the age groups. In order to determine the validity for predicting maximal oxygen consumption from stepping using a calculated platform height, three step tests were employed using one platform height and stepping frequencies of 22, 26, or 30 ascents/min. Each of the tests was administered to 93 6- to 18-year-olds. Correlation coefficients between the 15-second recovery heart rate after stepping and maximal oxygen consumption measured on a treadmill were .80 at 30 ascents/min, .79 at 26 ascents/min, and .81 at 22 ascents/min. Each of the correlation coefficients was significant at the P less than .01 level. It can be concluded that the model is valid for standardizing the platform height for children for use with a single stage step test for estimating maximal oxygen consumption.