The present study was designed to, determine how the magnitude of differences between the recall scores of intentional and incidental learners might be influenced by variations in the rate and number of presentation of stimulus materials. The stimulus list consisted of 12 nonsense syllables which had 30-34 non-association value by Umemoto and his co-worker's norms. The Ss were 120 college students randomly divided into two groups (intentional and incidental) of 60 each. Each group was further divided into three subgroups of 20 Ss each. In each learning group, the list was presented only once at a rate of one item every 4 sec. to one Subgroup, and 12 sec. to another. And to the third subgroup, the list was presented three times, with a 10-sec. interval between successive presentations, at a rate of one item every 4 sec. An electrically operated memory drum was used to present the list. The Ss of the incidental learning group, as soon as a stimulus item appeared, were asked to record that item in any of the four, blanks on a sheet of paper on hand. This ‘orienting’ task was given as a kind of personality-test. Immediately after the presentation of the list, the Ss were requested to write down as many syllables as they could recall in accordance with the original order of presentation of the items. The Ss of the intentional learning group, on the other hand were asked tc, perform the same task with the Ss of the incidental learning group, and were also instructed to memorize as many syllables as possible in the serial order of items. The method of the recall test for this group was identical with that for the incidental learning group. As the results, it was known that the differences between the recall scores of stimulus items of intentional and incidental learners depend on the rate and number of stimulus presentations: when the list was presented only once at rate of one item every 4 sec., no difference between the scores was found. In the case of slow rate or many presentations, however, the scores of intentional learning was reliably higher than those of incidental learning, as a result of the improvement in the scores of the former in spite of no improvement in the scores of the latter. The improvement in the scores of intentional learners on the present occation is mostly attributed to the increase of rehearsing-effect of stimulus materials. This result confirms the findings by Saltzman and co-worker's experiments in which the recognition- test was used, and suggests obviously that it does not necessarily make learning beneficial to have the intention to learn the stimulus materials.