Two experiments were designed to separate the effects of oral repetitions from those of covert mental activity in over rehearsal on free recall. In both experiments, subjects were visually presented several lists of eight noun pairs one by one, with asterisks under the left or right noun of each pair. Subjects studied the lists by observing both nouns of each pair as well as by rehearsing aloud one noun with/without the asterisks. Each of the list presentation was followed by oral free recall test of both rehearsed and not-rehearsed nouns. It was expected that the difference of recall between rehearsed and not-rehearsed nouns would indicate the effects of the repetitions but not of the total rehearsal activity including the covert mental activity. In Experiment 1, the time lag between the study and the test was zero or 30 seconds. In Experiment 2, the time available for rehearsing each noun was four or eight seconds. The results suggest that the repetitions have only STM-maintenance function whereas the covert mental activity has only LTM-construction function.