The development of the ability to establish and maintain balance is claimed to be an important prerequisite of almost every movement task. Accurately measuring children’s balance ability is important to effectively assess motor performance. Advances in technology have created comprehensive measurement systems that provide the ability to measure movement through ground reaction forces using force platforms. Although these instruments have been used in numerous studies for children in recent years, validity and reliability evidence has not been well examined for children. Therefore, the purpose of this study was examining the psychometric properties of static and dynamic balance performance measures in children 5 to 9 years of age using the NeuroCom SMART Balance Master® System. Fifty-seven elementary-aged school children (42 girls, 15 boys) with no documented physical or mental disabilities performed a static and dynamic test of balance using left and right Unilateral Stance Test® and Tandem Walk Test®. Validity evidence was examined with correlation between balance performances and age, and reliability was estimated with test-retest reliability with twenty-nine children. Reliability coefficients were calculated from Intra-class correlation coefficients (ICC) using a two-way random analysis of variance. The results of this study revealed a significant relationship between age and balance performance for static unilateral stance on the left foot (r = -.40, p < .01), right foot (r = -.43, p < .01), and dynamic tandem walk’s speed (r = .43, p < .01). There, however, were no relationship between age and balance performance for dynamic tandem walk’s step width (r = -.23, p > .05) and end sway (r = .05, p > .05). The reliability coefficients of these balance measures also revealed that children’s unilateral stance on the left and right foot were ICC(2,2) = .84 and ICC(2,2) = .75, respectively. Also, the results indicated that the tandem walk’s speed (ICC(2,2) = .87) demonstrated an adequate level of reliability, whereas the tandem walk’s step width (ICC(2,2) = .57) and end sway (ICC(2,2) = .44) were low. Computerized force platform assessments concluded to be an appropriate method to measure static balance, however is problematic for dynamic balance in children 5 to 9 years of age. Keyword(s): measurement/evaluation, research