This study evaluates the agility of preschool children by measuring simple reaction time and repeated sideways jumps. It also examines the influence of video games and exercise on development of the agility. The subjects were 636 preschool children(315 boys and 321 girls)aged 4 to 5. They performed the simple reaction time test with light stimulation and the repeated sideways jump test for five seconds. The agility score was calculated from the total T-score of both agility tests. This study investigates video games and preferred play time for the benefit of parents and nursery school teachers. The test results show that 37.6% of the 4-year-olds and 36.5% of the 5-year-olds frequently played video games and 57.1% of the 4-year-olds and 61.0% of the 5-year-olds showed a predilection for whole-body dynamic play(tag, jump-rope, dodge ball, etc.). The 5-year-old children were superior to the 4-year-old children in both agility tests. The children who played video games well showed higher values in simple reaction time than the children who did not play video games, but not in the repeated sideways jumps. The children who like whole-body dynamic play scored higher than the children who like static play, not only in simple reaction time, but also in the repeated sideways jump test. Although video games affect reaction time of the upper limbs withrespect to visual information, there is no effect on agility for the rest of the body. Enforcing exercise and play time activities, however, would be an effective way to improve the agility of the whole body, in addition to the reaction time of the upper limbs.