The relationship of body temperature to movement and daily life in a nursery was examined in 181 children at a day care center, and the importance of body temperature to the life and health management of the children was evaluated. (1) The children were divided into three groups. Group A comprised 28 children (15.5%) whose body temperature exceeded 37.0 degrees at 9:00 a.m., and whose average temperature was 37.19 degrees. Group B comprised 127 children (70.1%) whose body temperature ranged from 36.0 to 37.0 degrees, and whose average temperature was 36.48 degrees. Group C comprised 26 children (14.4%) whose body temperature was under 36.0 degrees, and whose average temperature was 35.58 degrees. (2) Children in Groups B and C, whose temperature was under 37.0 degrees when they arrived at the day care center, showed a temperature rise after movement and play in the morning. On the other hand, the children in Group A, whose temperature exceeded 37.0 degrees, showed a decrease in temperature in spite of walking an average of 3209 steps per person in the morning, which was about 200-400 steps more than Groups B or C. (3) Keeping early hours, having regular bowel movements after breakfast, and walking to school help to raise children's body temperature when they reach school. This temperature increase assists mental and physical warming up, encourages efficient exercise, and aids better release of energy. If more steps are taken to improve the quality of exercise after 3:00 p.m. as well as in the morning, problems such as children needing snacks before supper or going to bed late will be solved. The children will become hungry after playing and will be ready to eat supper at the right time. At night they will feel moderately tired and become sleepy around 8:00 p.m.. Recently there has been a rapid increase in the number of children who tend to watch TV or play video games while eating snacks before their parents come home, and this is exactly what needs to be addressed in order to improve juvenile health in modern life. In conclusion, physical exercise and play are considered important in children for activating the autonomic nervous system, which controls body temperature.