Two selective free recall experiments were carried out as a function of the intensity of a voice presenting the items, in order to examine the effects of the physical characteristics upon selective memorization. The percentage of correct recalls was greater and the number of intrusion-errors was smaller in the weak intensity condition than in the strong intensity condition in the rear section of serial positions. The effect of intensity was not clear in the initial and middle sections. The results suggest that the intensity affects the first selection which takes place before short-term memory, but not the second one which takes place in the process of transforming the to-be-memorized items into long-term memory, which reflects the difference in the ways how these selective processes work upon the items. It was also suggested that such effects were produced by the intensity of the item relative to that of the adjacent items.