This paper considered the theme of conversation as the main supporter of the actual conversation, and examined various factors of conversation associated with the theme. First, with regard to utterance overlaps, the frequency of occurrence was significantly higher in the non subject group than in the subject group. However, with regard to the speech opportunity, there was no large variation among the groups regardless of the theme. Second, the major quasi - linguistic expression of oral language was divided into two parts: within 1~2 seconds and more than 2 seconds. In other words, only the latter was a significant variable among the groups. Third, there exists the related problem of the differences in the speaking length of groups according to the subjects. A significant difference was also seen between the group that assumed the theme and the group that followed ti.