Effects of the intermittent lights or sounds whose frequency was 2.5, 5.0, 7.5, 10.0, 15.0 or 20.0 cps, on time estimation were examined. The standard time of d sec was estimated by the reproduction method. Intermittent stimuli were given during the reproduced time. ,5s were elementary school children of the 1st and 4th grades and undergraduates. Main results were as follows: (a) Generally, the reproduced time was the shorter, the higher the frequency of stimuli was even under 20.0 cps condition. (b) This effect was the greater, the younger the subject was. (c) The reproduced tinges with intermittent lights were generally shorter than those with intermittent sounds.