We have demonstrated that the 10 min cycle ergometer exercise with the load as high as 60% of the maximal heart rate augmented the working memory estimated with using, either RST, or 2-back test in young people. These tests were conducted as soon as the exercise terminated. The present study was designed to know how long augmentation can be sustained after exercise. In the first, we investigated using RST if the augmented state was kept at 20 min after exercise in 14 young male volunteers. Subjects finished a 10 min ergometer exercise with loads in such a way that the heart rate attained 10, 30, or 60% of the predicted maximal heart rate. One experimental run was composed of pre-RST, exercise, 20-min rest and the post-RST. The interval between experiments was longer than one day with the order of exercise distributed equally among subjects in order to create a good balance. Mean result of RST after each exercise was compared with that before exercise with using a dually tailed t test. Only the RST after 60% exercise could induce a significant augmentation (p<0.025). Then, we have introduced RST after having 40 min post-exercise rest in 15 young student volunteers using the same protocol as in the first experiment. In this experiment, neither 15%, nor 60% exercise load induced significant increase, although probability of the t-test was decreased as low as 0.06 in the 60% exercise group. From present results, we concluded that the augmentation of working memory induced by a moderate exercise would terminate within 40 min after exercise. [J Physiol Sci. 2007;57 Suppl:S165]