[Purpose] Agility includes three factors: rapidity of reaction, rapidity of directional change, and velocity of muscle contraction. We proposed the Ten-Step Test (TST) as a new performance test for agility. In our previous study, the criterion-related validity of TST was evaluated by comparing TST with a timed supine-to-stand test which reflects motion speed. However, timed supine-to-stand doesn't include rapidity of reaction. The purpose of this study was to evaluate the criterion-related validity of TST using motor reaction time (MRT). [Subjects] One hundred fifty-two community-dwelling adults were recruited. [Methods] TST requires the subjects to place one foot at a time, ten times on a block 10 cm in height while standing. TST was conducted twice, and the quickest time of the two trials was used for analysis. MRT was measured as the time between a touch on the malleous and the response of the ankle dorsi-flexion in a sitting position. For evaluating the relationship between TST and MRT, the conformity of the regression formulae of aging changes and correlation coefficients were analyzed. TST was also compared with the Functional Reach Test (FRT) and muscle strength of the knee. [Results] Both TST and MRT showed a quadratic rather than a linear relationship with age. The single correlation coefficient between TST and MRT was 0.59. [Conclusion] Age-related changes of TST and MRT showed a similar curve. These curves showed a significant increase after the age of 50, and the correlation coefficient between TST and MRT was high. The findings suggest that TST includes a factor related to motor reaction.